I was paid got once by a Dr, two of the hundreds were counterfeit didn't find out till I was depositing it and the bank told me. The doc made it good, he got them from a patient who paid cash. It's not unusual for somebody to end with a fake bill unknowingly.
If you were black it would have been ok for three cops to sit on your back and neck while you lay cuffed, face down, in the street until you expired of unknown causes. Hell, maybe even longer as, in your case, it was for two supposedly counterfeit $100 bills.
