First of all, the developer should have responded to your email, so be persistent.
This is what I tell my customers to try in situations like yours:
1 Go to My World and tap the refresh button. Check both the installed list and the uninstalled list for the game. Re-install if necessary.
2. If #1 does not get results, click the purchase button on the game's download page. Since you have already purchased the game, you should see a dialog indicating that you will not be charged again. If the dialog pops up hen proceed with the re-install. It the pop-up does not appear go to #3.
3. Contact app world billing at the following address: firstname.lastname@example.org and tell them about the problem and the steps you have taken to resolve it. Forward your receipts as proof of purchase and indicate that you tried and failed to reach dev support. Ask RIM support to reset your account so that you can repurchase your app. They will likely issue a refund and tell you to try again.
Good luck and I hope that you get your problem sorted.