The fact that I was deleting 250+ GBs was probably a dead giveaway, but while trying to uninstall and delete the nonsense that resulted from Blackmagic Da Vinci resolve video editor installer dumping all of its files into my D drive x86 instead of into a separate folder, I accidentally somehow put my D drive Steam folder into the folder I created for Resolve, then deleted it when I assumed the install was buggy due to the folder containing 260 GBs...

Anyhow, now steam thinks the games exist but can't find them. The loss of the saved games/mods to redownload is annoying, but can ultimately be overcome. Is there an option somewhere to redownload everything that was deleted from a drive folder, or do I have to do it manually one at a time...?

Also, super big thanks to Blackmagic Design, super glad your CEO gets paid the big bucks to drop an installer than is like 18 years old and functions on the same as when it was on Windows XP...

Edit: After further research, it appears Steam's search functionality does not let one search by install location/install drive, so unless someone knows something I don't, the only solution is to do it manually. Hooray.