Somehow lost 30 GB of space

I got bored today and decided to download an old game, about 30 GB in size. My C drive had 50 GB so I figured its okay.

When the installation was almost finished, there was an error saying I didn't have enough disk space anymore so the installation wasn't completed. I checked and indeed I was left with 600 MG of space on drive C. I dug around a bit and found SOME of the data that was already installed. But now I have 22.8 GB of disk space left instead of the 50 I started with.

I searched my entire PC and there isn't any trace of the stuff I installed!!! I did a system recovery but it didn't help. Does someone know where should I look for? I tried REVOuninstaller and it didn't find anything.