I'm confused about how this happened at all. It's certainly an unhappy circumstance .
A:M does have an automatic incremental save option, but I've never used it.
In my own work i just never save over anything, I always "Save As" and manually increment a version number. I got into that habit back when A:M was famously unstable and I felt i needed to save every two or three minutes.
Now I save a few times an hour, usually after I have added some notable detail or right before I do something that will be hard to undo, as some plugins are.
I view the SVN as something for groups that collaborate over a network and need to be sure that everyone is using the same version of an asset.