Only one particular object didn't save?

Hey, so Ive been using animateCC for a few years now, and I know to always save multiple copies of what i'm working on in mulitple places. This didn't stop one particular object I had spent all morning working on from not saving (an arm that i added 5 new frames to) . Every other alteration I made to my project saved correctly, including things I changed after altering the arm, but the work I put in on the arm just vanished. Did I do something wrong, or is this just another one of adobes tendancies to corrup and loose data?