Ok, I'm recognizing that this couldn't be done individually, so there is always the slim possibility of the one-in-a-million case of someone total, completely, without reservations, truly wholly oblivious that something was wrong, someone so green to the game that it never ever occurred to them that maybe it was too good to be true, they never realized so over time and never heard any comment about it at all.
For such extreme outlier cases it sucks, but unfortunately bugs are still par for the course in private servers, their existence is something anyone playing in one is implied to understand and accept. Most can get fixed and sometimes the fix won't be painless, but there's no objective way to separate who was so clueless to neither know better nor wonder if that was working right. OOFMAN's sarcastic post pretty much sums it up: suddenly everyone was an exception and didn't know; for someone who would abuse a bug, lying about it is nothing.
Now what?