How to check if EOS tokens have a public key?

Hi all, newbie question!

I hope you can help me. I have participated in the EOS ICO, but I'm yet to claim my tokes and register my public key. I also decided to purchase some more EOS on Kraken last night. My question is not about how I go through the process - I get that but it's more around what happens when I merge the two?

Let me explain why: I read somewhere that if people don't register their public key then the tokens are worthless in June 2018 when they go over to the EOS blockchain. So I guess my question is: do exchanges like Kraken check whether there is a public key in place before you can trade them on their exchange? If not, is there any way to find out which tokes have / don't have a public key registered? I'd hate to find out that the lot I bought yesterday is worthless after June 2018...

Thanks for your help in advance!
Jeroen (aka The Transparent Trader)