iMovie crashed while transferring project — how to restore what may have been lost?

I'm using iMovie 10.0.3 on a MacBook Air. I started a rather large project and the library took up considerable space, to the point I got warnings. I connected a compatible drive, created a new library on it, and moved my enormous event/project-set to it.

In the middle of the move (the activity indicator pie was maybe one-fifth full), I examined at a different, local project, thinking I should keep looking at iMovie in case it had something important to tell me. This turned out to be stupid — as soon as I made a tiny change, iMovie freaked out that it couldn't save the change, and I (even more stupidly) hit Quit because it was the only option in that message. Quitting ended up taking precedence (I guess the developers never considered forcing it to obey the activity meter, kill the change I'd made, and stay open until the activity was done).

The end result, looking at each library (the local and the external) is that their total GB is much less than the total was originally — a lot of data has simply gone. (At least I don't have to worry about the maxed-out local drive anymore.) The thing is, I still have the original source files for the events around. So I'm crossing my fingers that the project files, being by far the biggest expenditure of my time (but of course much smaller in size than the events), were successfully moved over and can be reconnected to the large event files. I have reason to think this happened, because I reopened iMovie (probably the third stupid thing) and the project looked like it was there with all its trimmings. It just crashed a few seconds into playing it, which I hope was due entirely to missing footage and not corrupted/missing project data.

How do I go about fixing this?