My saved pdfs disappeared from my drive!

I worked on several pdfs yesterday. Saved each one in a particular folder. I close the computer for the night. Next morning, "pdf can't be found" (even when I try to open the file directly from Adobe's "recently opened" dropdown list). The folder no longer has any of my files!

I do a test pdf called "test". Save it in same location. I see the file there, as I did with the ones I created yesterday. I restart the computer.

Poof! Disappeared again.

Fortunately, these weren't precious documents. But I did lose 6 hours of my life.

Help? What's going on here?