Finding error notes

Has anyone found any error notes in circulation? I once cashed out at a Sears Hardware store and received 3 brand new consecutive $1.00 bills. I noticed that on the backs there was a progressive gutter fold going from a pencil line to an 3/16" fold. I headed back to the store but they had already locked the doors they were closing. I never got the chance to look at the rest of the notes in that stack.