Android :: Market Loses Track Of Purchased Applications After Factory Reset

I've had several of my users email me to tell me they had to do a factory reset on their phone for some reason or other. The problem is, they had purchased apps installed and the Android market app loses track of this information when the phone is reset. My only solution to their problem is to go into my checkout account, refund their money and ask them to repurchase my app.

Am I correct in assuming that Google decided to only check the PackageManager on the device to determine if an app was purchased or not? Is there really no other means of determining that an app was purchased? Surely this information about the purchase is kept on a server somewhere (which is why I can see the purchase information with Google Checkout) Also, since the user of a phone must login with a Google account in order to use the market, can't you just correlate the user's purchased apps with their login account and bypass the phone altogether? I'm probably missing something, but I wanted to let you know its a source of frustration to have to deal with this when I consider this issue the responsibility of the market infrastructure.