Can't find downloaded App on iMac.

My son was playing Angry Birds on our iMac (2010 running 10.6.8) when he came in and said there was a problem with it and he had to put it in the trash. I tried to do standard things (remove from trash, delete and restore from Time Machine, reboot, etc) and nothing. I kept getting the message that the file was damaged and I should delete it and redownload it from the App Store. So I go to the Purchased tab, and there it is -- I hit "install". The progress bar shows it installing. I see it on the dock loading up.

However, once it's finished, I cannot find the app ANYWHERE on my system -- not in Applications, not using the search function, not looking on any of the drives directly. I looked at the App store -- this is supposed to work on my OS and it was working a few hours ago. I have deleted and redownloaded several times now -- each time it shows it "installing" and if I go to the app store, it says it's "installed".

Any ideas where the app went to or other hints?