Usually when I'm done with an illustration, Illustrator on the iPad will automatically save my work when I press the "back" button. I did that with the most recent illustration I've been working on and it didn't save at all, and I lost a day's worth of work. Is there a way to recover the illustrator file?
I don't think so. Aside from the fact that without exact info on your mobile device and other stuff this would not be going anywhere, it would probably be impossible to figure out what exactly happened. You can of course always try and check your CC storage via a web browser or using the CC app on another computer. Maybe you can find at least some older version that way.