Did you recently make a change here: Preferences > Project Files > Trigger 1st preset when you open a project?
I had unchecked that (thinking I was doing a smart thing) and forgot that projects are based around presets because I rarely use presets. Of course you can trigger a preset once the project opens, but if you're not used to doing that you might be in for a surprise when your Layers window is empty on every project you frantically try to open... thinking "what? these were just working yesterday!" and forgetting about messing with Preferences earlier.
If you didn't know, now you know, so don't be a dummy like me and submit a bug report over something so silly.