Project is suddenly gone from Database

Hoping someone can help me out. I have no idea what happened. I rendered part of my timeline, it completed with no issues. I saved the project and I exited Resolve. A few hours later I opened Resolve and none of the projects were in the Database. There was no crash, I didn't move or delete any files. I've been coloring this feature for a month. Has anyone had this happen before?

Working from internal drives only?

No I have everything on external drives.

[Peter Chamberlain]

Did windows change your drive letter so the path to the DB no longer exists?
Is its an ExFat drive you also might have trouble recovering too.

everything on external drives.

That is like playing Russian Roulette.

Just...don't.

The database should definitely be internal.

I got along for several years with an external Disk Database, but I recognize that it's dicey because of the risk of even a split-second disconnection by the OS. And external drives do spin down on occasion to save power and prolong life.

We're currently using an external system as a PosgreSQL server, but it's a 4TB SSD and has been extremely robust so far.

To the o.p.: to guard against even the slightest chance of database failure -- which in my experience is extremely rare -- always export a backup copy of the file every day. You could also use the autobackup utility within Resolve, and there are instructions elsewhere on how to use those. The advantage of doing it manually is you can choose how the backup file is named and where it's stored, plus it's a portable file you can upload to the cloud or keep on a thumbdrive. I've only had to use backup session files maybe 4 times in 12 years, but it does happen.