I restarted my computer and opened ST2 which also seemed to have an old copy of a file that had since been edited in ST3.

Accidentally saved which of course overwrote the file so when I opened in ST3 have lost a few days of changes. Unfortunately not backed up…yes, I know.

Does ST3 retain a hidden cache that I can recover the file from? (which ST2 seemed to hence it did not load the file that was last saved with ST3)

Steve

The “hidden cache” is merely the session restore feature. If you close Sublime with an unsaved file open, then it’ll remember the unsaved state (hence the lack of reloading the ST3 version from disk). Other than that there’s nothing you can do.
I’m not sure why there are two threads about this on the same day, but I’ll recommend the same thing to you as I did over there: github.com/vishr/local-history