Q: App not available again

Does the app appear in your purchases list.  If it does you should be able to download it again;if it doesn't would indicate that you haven't bought it.    In that case you will need to get on to Apple, though there is always a possibility that the reinstall caused it to become hidden.

iTunes Store: Hiding and unhiding purchases      If that doesn't find it go to >

Troubleshooting the Mac App Store    And your last option is >

How to report an issue with your iTunes Store, App Store, Mac App Store, or iBooks Store purchase