Fresco has been crashing a lot for me lately and has even been deleting my progress. Strangely enough, I checked the timelapse and it has still recorded what I had done even when the progress in the actual drawing is gone.
Try to look in version history when was the last saves and look into "technical help diary" that is located in preferences/help. You can download a text file. That can be problem with fresco logging into your account after crash. I same cases (for instance after upgrade of fresco) you not logged to your cc account and program restictes syncronization, i.e. it overwriting you current state of work with last saved file from before crush. Check the time on versions history. In such a case in tech diary you will find line like: "sync restricted".
I know if you're using an iPad, you can share crash reports with the developers. But as Sjaani asked, what device are you using? Also what storage capacity do you have. I know with iPads if you're running low on memory, things can act a bit squirrely