Cat/kittens and their toilet behaviors
Rewind a few months, thinking back about a discord chat with 
I told him we never had any issues with cats or kittens and their urine. If you keep a very close eye on them at the start of their lives, it's not that hard to avoid accidents. In our experience, one mishap, an immediate clean-up with a tissue or kitchen paper, and then adding that to the litter box and they get understand what the deal is.
To be fair, I totally expected this thing to be much more complicated with Mojo and Mochi, picked up from the streets, with no experience using a litterbox at all, but I was wrong, even with them it was just 1 pee to make them understand where to go to the toilet the next time.
All kittens fostered arrived here trained to use the litterbox so we didn't have any issues besides a little accident here and there when the parasites made them poop over the edge or three was a crowd in the litterbox.
The accident
So far so good, I proved
So I only closed the blinds there when we were out as well as during the night because I don't trust the youth that hangs on these stairs one bit, I can totally see them throwing a burning cigarette inside while drunk causing a fire while the kid is sleeping there. And my workspace is below the window so I'm careful having that window open. So throughout the day the door as well as window are open while I use the fan to blow air through the room. So far so good until last week.
I walked into the room and I was blown away by the smell of cat piss, while the kittens were all inside there was a clean litter box in the bedroom only. Shit! It was almost midnight what great timing to find out. We had to put on the light to investigate and mop the floor, hoping it would be ok for now. It was ok to fall asleep but waking up was not that great, lol. The smell returned.
Throughout the day, everything was open and the smell went away, we both searched and searched in every corner, on every item in the room, the matrasses, etc, you name it. Every time when the door was closed for an hour and the blinds were down, the smell was unbearable! I went nuts, let me tell you. Like freaking out as now it was already 30 degrees throughout the day and you can only imagine how that adds to the smell!
Out of options
We have this bottle that breaks the enzymes of the pee if you put it on the spot pure, then remove the liquid and wait for a day to wipe it off. But this stuff only works if you put it on the spot pure and to be able to do this, you need the spot where they had the accident. I thought I found the spot twice going by Aki's nose when she was smelling for a bit too long to my liking on one place and decided to take my chances and use the cleaning stuff on that area. For a few hours at least I smelled the cleaning stuff instead of urine, lol.
The search continued
I had some laundry on the top bunk bed as well as clothes that I yet had to check later and went through every single sock and piece of laundry on there. Everything got sniffed thoroughly lol. The floor got mopped several times to make sure no spot was missed, and yet every time when the door had been closed for an hour, we'd open it to smell it again. So strong! How is it possible that we can't find this?
I swear I was losing brain cells over this mystery because while I was working in the room throughout the day, with the window open and a mosquito net in front of it, plus the door of the room not closed, I smelled nothing. Neither if we entered the room. The kittens smelled it every time they entered so at some point I tried to keep them out for a few days until this mystery was solved as I was afraid one would find the spot before we did and make it worse.
The weather made it worse
Imagine 30+ degrees Celcius and a cat urine smell, it's not nice. That's the understatement of the year! I already saw how this smell came from the mattress while there was no visible spot and we'd have to buy new mattresses soon to solve it. Then I realized that I read somewhere you can find these spots with UV light. Thanks to my friend G.oogle, I discovered this was correct, you just need a certain strength in light and then it will light up when you shine at the spot.
My boyfriend said it will be hard to find one because this is not the regular store item here, he said he was looking for it in the past and couldn't find it either. To my regret I saw online hits, taking weeks from China, some other stores here sold it as well but taking up to 5 business days to get it at home, and more expensive as well. I was not going to have this for 5 more days so we went to the animal stores in person to hear it was online only. As it was Friday, I might as well try to figure it out otherwise we'd buy a 3x more expensive UV light while the problem was solved already. Meanwhile, I tried using the UV light for nails I have (assuming it was not strong enough, but hey, at this point I was willing to try everything, haha) without any success.
A bright moment
My boyfriend was the one with this bright moment, he said what if it comes from outside and a cat has been spraying there in front of the bedroom window? I realized he may be right as Ginger (Mochi's redheaded cat friend who we call Ginger) had been sleeping in front of this window several days after Mochi was found dead. He may have marked this spot as his territory.
We removed the mosquito net, closed the window, and put on the air conditioner. He went outside to check if he could smell it over there and he said it was smelling as if it came from inside the room. A little disappointed at this point that he could not find it exactly but we decided to keep the window closed and have airco at night instead of fresh air. Guess what? In the morning, no cat pee smell! Guess I was lacking oxygen all along but sniffing up cat spray from outside, yuk!
I'm so happy he figured it out as we never once thought about this option as it didn't happen before. We went away most of the day today and came back without smelling anything, mystery solved! I hope we can properly remove it from that spot in front of our window, if it doesn't work right away I will just have to deal with it for a week or so while we wait for that lamp to arrive. So be it.
Have you ever had a similar situation? How did you solve it? Were you also losing brain cells over this mystery?