This is a very weird problem, and has never happened before.
I have auto saves set to every 2 minutes, because premiere crashes a lot for me. I was working on a project for 2 hours, and I saw the auto save window and bar pop up many times. Then premiere crashed, so I opened up the project again only to see I lost 2 full hours of work. I checked the project file, and the existing auto saves, all of them said last modified: 2 hours ago. I have no idea what happened, and this is very stressful. I can't seem to find others with this problem, and I have no idea why it happened. That was the only sequence opened at the time so it wasn't saving a different sequence or anything. This makes no sense at all.
Do not rely on autosaves, Autosave in Premiere Pro has never been reliable.
Save different versions of a project as you go along at regular intervals to a backup drive different from the drive on which your projects are located.
If your project is corrupt without you knowing so will your auto saves be.
As Bob says: do a Save a Copy on regular intervals.
Make new project and import old one: see how that goes.
Well, looks like my progress is lost, but I'll be sure to actually save more frequently next time.