SAI 2 added file recovery apparently like 2 weeks ago.
I did a quick scribble test and closed SAI through normal quit means - I opened it up, went to File > Recovery Work, and I get to see and recover it.
Did it again to the same document, apparently it’ll even remember your operation history (to as much as SAI normally remembers ~100 I forget) which is nice too.
There’s probably lots of intricacies, I’m not one for testing it all, but this might save like 80% (if not more) of situations such as forgetting to save the source file or something too.