Text gone missing?!

I have an article draft I’ve been working on for two years, a series of folders with subdocuments. All the text (about 1500 words) from a subdocument has entirely disappeared. It’s just blank. There are also no snapshots. Now, I have this in Dropbox Pro, so I can roll back to an earlier version of the subdocument somehow, but I can’t figure out what’s what among all the data folders named things like 3FA62546-6576-ETC.
Any suggestions on how to recover this subdocument? And why it disappeared?

Edit: Dropbox has several empty data folders, but also shows now deleted files in those folders over the last 30 days, and I could swear I’ve seen this section more recently than that.