I'm wondering about how this note could had "fell" into anhydrous ammonia...
For those who don't know what is anhydrous ammonia, it's the pure gas ammonia which can be condensed into it's liquid form, but it' fairly cold: -33°C at it's boiling point. Not to be confused with the solution of ammonia sold in the commerce (which contains water). It's not the kind of stuff you can get at the local hardware...
So if you soak a note in liquid anhydrous ammonia and remove from it, the liquid will evaporate quickly. The note isn't really "wetted" because there is no water present. I think that this note cannot have fell accidentally, but soaked deliberately, maybe just to see what will happen when you soak a note into dry ammonia (by simple curiosity). The shrinking could be caused by a chemical alteration of the paper by the pure ammonia. If I had anhydrous ammonia on hand, I would try this experiment myself (and gladly post the results)
.