I'm sorry for your loss, OP. It seems that the Thunderpick is no longer active on the forum, and if you check their account, they already have negative feedback related to another unresolved scam accusation.

Thunderpick.io SCAMMED ME FOR 1049€
Unfortunately, it looks like resolving your issue through the forum might be unlikely.
However, you could try reaching out to a mediator like AskGamblers. They might be able to help.