Hi Stolen from,
You are probably looking at the wrong "Purchased" (confusing, I know). Click on the iTunes Store. Once the store is open, click on Purchased under Quick Links. Once you click on that Purchased, you will see a window with several tabs (Music, Apps, TV Shows, etc.).
Click on the Apps tab, and then click on "All" or "Not on this Computer". Anything that you do not have downloaded to that computer will show up with a little cloud next to it. You can click on a cloud to download, or you can click on Download All at the bottom to download all of them.
Cheers,
GB