I'm sure I remember coding a fallback for specifically this case; with the behavior being that it would get as close as it could. (ie: Let's say the last level played was a level in Tricky of Orig; if that level is now missing, it'll go to the first unsolved level, or maybe just the first level full stop, of Tricky; if the entire Tricky rank is missing or has no levels, it'll go to the first of Orig as a whole; and if the entire pack is gone, just to the first level you have in your levels folder)
It'd seem though, either I only thought about doing this, or it broke at some point.