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)