File Corrupted and Crashing (but not yet beyond repair)

Hello,
after a 7-hour working session without any saves, (my fault, although I wasn't even aware file corruption was possible) I restarted the app after downloading a new soundfont. My project, however, crashed upon opening; the crash reporter empty. I looked up an oft-used procedure - change the file extension to .zip, etc., but I don't know where to look for corruptions or what to do next (also finding out that in some cases of file corruption, the .zip file is not openable either). It's not an urgent matter, but I'd greatly appreciate any help.
Best regards