I have been using Gas Cubby Free v 2.7 on my iPod Touch 5th gen, iOS v 7.1.2
I don't use the app that often as I don't put gas in the car all that often since it doesn't get driven all that often. However, I do use it.
The other day I finally updated my Touch to iOS 9.2.1 (from 7.1.2 - I missed iOS 8 completely).
Today I noticed that Gas Cubby was no longer on my Touch. It was, however, in my Purchased Apps. There was also another app that was in Purchased and no longer on the Touch. I had never noticed this before after updating iOS, but didn't think too much of it. I just downloaded back onto the Touch. When I opened it, however, there was no data at all. Nothing, Nada, Zilch. Fortunately I do have a backup of my records in both excel and cvs. But I don't think there's a way to import them to my app, is there?
And why would it not get restored back to my Touch after updating the iOS? Anyone else have that problem? The other app didn't contain data so I can't compare to it.
Since the Free version of the app did not have online sync, there isn't a way to recover that data you had in the app. The data was stored locally and deleting the app (even if Apple updates did it for you) will purge that data unfortunately.
Hang onto your CSV. You can import it into Fuelly if you'd like.