I found a $100 bill, took it to my bank and it was counterfeit - will I get in trouble?

I was at a laundromat washing a bunch of clothes from my store. I put the clothes from the washer into the dryer. When I went to get the clothes out of the dryer I saw a $100 bill that was slightly damp right in front of my dryer. I thought maybe it dropped out of one of the pants I was washing and maybe I just didn't see it ---- but that seemed unlikely so I asked the other person that was there at the time and he said no it wasn't his so I took it to the bank later that day --- my bank. It turned out it was counterfeit ---- I thought it was odd since when you held it up to the light there was a line showing through it and the face of the president on the one end like it's supposed to be. I told them I had found it while doing laundry which was why it was damp (it had since dried up but was crumpled). I said OK I'd tear it up right then and there and throw it away. Out of nowhere came some other teller who was "roaming" she must have been a manager, although she wasn't the bank manager. She said No --- you can't tear that up - she told my teller I had to initial it and the teller had to initial it and put my account number on it and send it somewhere. I initialed it but told my teller I didn't want my account number put on it. I didn't want to get in trouble for this. She shook her head and said no ---- I wouldn't get in trouble and indicated she wouldn't put my account number on the bill. However, if a manager told her to do it, I don't see how she could not do it. Will I be investigated by the federal government for this phony bill I found? I had seen a phony bill before but this didn't look anything like the phony one --- I thought the color was off because it was damp. They never tested it or wrote on it with the "counterfeit" pencil sometimes they use - they just looked at it. Please help --- I'm a nervous wreck!