I can't speak for you because I do not know were you are. But if it were here in Zone 5b, Maritime Nova Scotia, Canada, I can confidently say this was clearly the work of the masked bandits: racoons. They are very capable of cleaning out an entire tree in one night - the night before the day you planned to harvest them yourself. They did it to me.
Of more significance, however, is how to avoid it next year: all that is needed is a low electric fence around the trees. I use 2 ft. lengths of plastic conduit driven 6 or 8 inches into the ground and strung with 2 strands of electric fence wire. (I was talking to somebody 2 days ago who uses only a single strand about 6" off the ground.) Racoons cannot jump, but they are adept climbers, and their little hands are excellent conductors of electricity. One note of caution: they are also damn smart, and, once they catch on, will time their attack by listening to the "thunk" of the fencer, clambering over immediately afterwards, before the next jolt. (I have my fencer set up in the closed greenhouse, where they cannot hear it.)
Broomholm OrchardZone 5b in Nova Scotia