ValM The App Store doesn't appear to recognize I have anything other than a free trial.
My bad, I just didn't think of an addition reason for this problem: @ValM purchased StitchBuddy 11 years ago, when it wasn't distributed through Apple's App Store, yet. This explains why her purchase couldn't be restored and the reinstallation didn't hold any purchases.
The solution is easy, and early customers just need to contact me with their registration details, and I'm happy to help!