iMovie '11 cache/HDD space

Hey guys, I have had something arise and was wondering if anyone here knew about it.

I was optimizing a video to do a Fast Forward effect, and the process took about 10GB of space for a 30 minute HD clip. Now I am using an 11" MB Air with a 128 SSD, so space is crucial. I started with 25.87 GB free before I began the conversion, afterwards it was just over 15 GB.

Now, the issue is this: when I deleted the project, my available HDD space didnt return to normal; it ended up being just a little over 20 GB. I checked the Cache folders, the App support folders, the iMovie projects folders, everything I can think of, and I can't find anything else to delete and now I am stuck wondering where in the hell that 5 GB is being used at?

Does anyone have any ideas or anything that I can look into to figure this thing out? I didn't even start the export/fast forward effect, I just deleted the project right away. Can't find any files on my computer though.

Zach