My guess is that the autosave was lost if the crash occurred while it was being rewritten. Probably bad luck and timing.
We've had a couple of occasions where the auto-saved file did get overwritten but because of the crash, the file contained zero data.
FWIW, Moho's autosave system
usually works, but I wouldn't depend on it as the sole 'safety net' when I'm working on something important.
Some tips:
When I'm working,
I'm always making incremental saves of my scene files (i.e., s001_chars_01, s001_chars_02, etc.,) and I probably a save a version about two or three times an hour, sometimes more. This way, I never lose more than 15 or 20 minutes of work if a scene becomes corrupted, lost, or I just seriously goof something up.
It's not uncommon for me to create many dozens of versions of a scene, so if my scene directory gets too cluttered, I'll drag a batch of the oldest versions into an 'old' folder. I don't like to delete these files while the project is active. Once the project is done, then I'll search for those 'old' directories and delete them.
I do this whether I'm working on a personal project at home or on a TV production at work. At work, we also use Window's Previous Versions (mentioned earlier,) but I found you can't really count on that system to save you every time either.
For me, getting in the habit of creating incremental saves is the best security there is. And I don't do this for just Moho, I do this with any program I'm working in. Accidents happen and you can't prevent that.
I kinda wish Moho did incremental saves automatically. The 3D animation program I use does that and it's saved my butt a few times. I know some users like that to be an option though because autosaving large scenes can slow things down on some networks.
Anyway, I know this info doesn't help you get your work back but maybe it will help prevent a disaster in the future.