It's the same situation whether the save is automatic or manual. Any data since the last commit is at risk. Not only might the data not be saved, your file could be damaged as a crash in "mid write" is the worst possible time to have a crash. FileMaker Server provides better protection against such a crash, but if you are hosting with FileMaker Pro or this is a file that is not hosted at all, it would be a good idea to use recover to check the file for damage after such a crash.
PhilModJunk and DavidAnders,
Thank you for the comments and links. I really appreciate it.