Double check all your devices. Did you ever use Keychain on a cellphone that still has it installed?

Check any auto back up to cloud service you have either used or came with any device/OS that had your keys on it. Some in the past have discovered there keys were being stored on a cloud service without even realizing it.

Do you still have the device you were using back in the day? Check to see if it’s still logged into anywhere with the active key. Steem had quite a few forks back then and everyone use to go raiding/farming for a little extra cash. Some sites have a “reveal private keys” and never had anything like a Keychain to use.

Think back to how you originally created your Steem account. Where you sent keys via Email? If so go check to see if that email is still around or if there is a way to request your email data going back 10 years from that provider.

As far as Splinterlands. What other blockchains did you connect to your account? I know at some point they added in ways to further lock down your assets. Maybe you have some kind of access still on another chain to move/delegate to another account.

1. Not all crypto games are as secure as Splinterlands. See if any assets in other games can be moved to another account with just the posting key.