Walking through a park, I noticed the corner of a $100 bill. Just the upper right corner, maybe an inch square, total. Picked it up and didn't think much more of it - just something to chuckle about and think "bummer - wish it had been the bigger part!" Continued walking. Found another piece. About 2/3 of a serial number on it. My interest increased, and I started actively looking for more. Long story short, about 15 minutes later, I'd found another 8 or 10 pieces - Everything *EXCEPT* Ben's face. Never did find that bit, but got exactly zero argument from the fellow behind the counter of the little package store I was a regular at when I asked him if he had a roll of scotch tape - Pieced it back together, taped it up, he rang up my pack of smokes and six pack of beer, dropped the (de)shredded bill into the till, gave me my change, and that was that. Couple days later, he told me the bank didn't even blink when he took it in and deposited it with the rest of the day's take - just tossed it into the "damaged bills" box and kept counting the cash. Best theory: Somebody dropped it, and it got hit by a lawnmower.
Years later, I was working a job that included picking up the garbage from a fancy-schmancy restaurant. They used clear garbage bags, and as I was unloading the day's pickup into the trash-masher, something inside one of the bags caught my eye, and I damn near went into the crusher trying to stop the "fling" I was in the middle of. Second closer look appeared to be a $50, folded into quarters, and glued to the inside of the bag by what looked liked might have been hollandaise sauce. First thing that went thorugh my head was "can't be real!" Next thought was "I didn't know they made those to look like fifties...", thinking about those little pamphlets that look like a folded up 20, until you try to unfold them and find out they're actually a tract that usually starts out something like "how much is your soul worth", and go on to try to convince you that the Big Juju in the Sky exists and loves you. That was when I said, Screw it", ripped open the bag, and grabbed what I saw. Unfolded it expecting a sermon - first unfold - "Wow... they really went all out on this one... Looks real!". Unfold again, still expecting the sermon. and instead, find myself looking at the front of a damned realistic-looking fifty dollar bill. Turn it over, and the back looks just as real. Rinse the gunk off it under a nearby hose, and sure enough... If it ain't real, it's the best fake I've ever laid eyes on. Finished unloading into the trash-masher, pulled out, and stopped at a walk-up barbecue place I used to like, bought myself a sausage and a drink, paid with the still moist 50, got my change, and away I went. Yay

Best guess: Somebody had left a tip (it sure wasn't enough to be intended to pay the bill - a typical 4-top in that restaurant would run up a tab in the $250-300 range before you started counting drinks and dessert), the waiter/waitress didn't see it when clearing, and scraped it into the trash can with the rest of the debris from dinner. Their loss, my gain...