Okay I thought I'd cleared this up but here we are with the same thing. This is almost redone again from the beginning by tracing and yesterday - not a problem. Today, a problem. This same piece of work was present on the side, I wasn't bothering IT, and IT wasn't in my way, I just had it clicked as invisible. The project Im working on is pretty much unrelated and has been saved and auto saved dozens of times yesterday.

If u can maybe get the glitch again, explain like Im 2 yrs old, take a screenshot, be very specific, whatever u ca - I'd appreciate it cuzz I don't see a mask or empty layer. Maybe Im not understanding you...