Known installed games suddenly vanish a day later

[Kougar]

I'm getting really fed up with steam's bugs and idiosyncrasies, including this one. Friends invite me to a game of Dota we haven't done in a week, and I find out Steam no longer thinks Dota is installed.

I tell it to install the game, and it discovers the files... then downloads a 3.5GB chunk of them even though I had launched the game a few days ago. I miss another game with friends while I wait an hour for the DL... and this isn't even the first time Steam bugs out and "lost" a game. What gives?

This isn't the Windows 98 era anymore... Steam has a dedicated SSD, Event log is fine, and there are no disk errors or issues. Haven't had a blue screen in recent memory and the system tests as stable.

[Ineffable Anathema]

Recent game updates - including various language packs - are likely the cause. I've had five of these mysterious game "uninstalls" and then "reinstalls". I did neither myself. If you check your available disc space while they are 'uninstalled' you will find that it does not change when they become 'installed' again (or not by very much if it does). Some of these 'uninstalled/reinstalled' games now no longer load, in addition. I have no idea if my saves for Dark Messian, for example, are safe because I can't get into the game.

[Kougar]

Yes, the disk space doesn't change and the files are all still there. Which makes it all the more infuriating when downloading them for no reason whatsoever, especially 3.5GB worth of them.

If you're having other problems such as launching them I'd suggest file verification scans and making sure the disk isn't throwing errors in the event logs, but beyond that you might actually have to delete the files and redownload them again to make it work... had a recent update break my TF2 alt account in a similar fashion.

[Ineffable Anathema]

I'm noticing thread after thread of people reporting games not working or launching. I'm convinced these updates are at the heart of the problems.

[Kougar]

Could be... personally can recall at least five friends that have bought games had had launch issues with games refusing to start regardless of the standard litany of fixes that usually resolves it. Seems to take a day to clear up...