Just upgraded to Mountain Lion and I have to buy iPhoto again?
Solution 1:
Since you've never purchased it from the App Store, you cannot re-download iPhoto from the App Store (unless you buy it again).
The only way you get re-download rights to iLife on the App Store is if you either purchased it from the App Store or bought a Mac that does not come with a software re-install disc.
Solution 2:
You can always re-run the disc based installer and avoid re-purchaing the app from the App Store. Eventually you will buy a new Mac which will then allow you to claim the App Store licenses for iLife without paying additional fees.
I'm stuck in the same boat with Aperture. The convenience of the App Store isn't enough to make me want to re-pay for the software I have a DVD based install.
Solution 3:
The same thing happened to me! I didn't have a disc and didn't want to pay for it on the App Store so I made a Genius Barn appointment. I explained my situation and they pulled out an external hard drive with all the software on it and re-installed it for free. If your close to an Apple store and have enough time, I would try that.
Solution 4:
You cannot download it from the App store. Once installed from the disc, you get free updates though.