I had a similar experience. I was a bank teller (credit union actually) back in 2006 and had someone come in with suspicious checks that he said he desperately needed the funds from for paying basic cost of living type bills. There was the whole nine yards about kids to feed and so forth. I waived the hold and then the checks turned out to be fake. They got away with it as far as I know and I got in big trouble.

Here's the super interesting/embarrassing part! Just this week I had a hold on a check. I knew I wanted to convert the cash that I didn't immediately need into bitcoin. I was comparing what I could get from the preview transaction of a couple of exchanges yesterday and actually accidentally hit the buy button on one of them! After a super embarrassing email exchange with the exchange (repetition not intended :) ) last night, I finally just called the bank today and asked them to have pity on me and let the ACH go through. It looks like I'm going to make it out with just an overdraft fee and not the whole ACH reversed.