My frames are there but the drawings are not showing up

I’ve been using Toonboom mostly as a tool for drawing and don’t really use the animating tools. I have a file which I use to draw a lot of my stuff and semi-recently started working on a new file since the old one got too big. There was something I needed to reference from my old file, but when I opened it up all I can see is the default grey screen, with none of my drawings showing up, nor the colors. I’ve checked that my layers aren’t hidden, and have tried to restart Toonboom, but the problem persists. This is the only file where I have the problem. Is there something I can do to recover the files?

update: as I went to fetch a screenshot of the problem, it seems that the drawings have reappeared. I’m still curious as to why it happens, though. If anyone knows why this occurs please let me know!