App store sign in when offline!

Yesterday, whilst on a train (a 9 hour journey) I tried to use an app previously downloaded from the app store. It refused to run until I signed into the store but, being offline, I couldn't. Luckily, I could connect online via my iPad (once we were passing through a good 4G zone) and was able to get the app running.

However, if I was working abroad (or anywhere without an internet connection) a recurrence of this would stop me working. I might as well be using a Chromebook if I can only use apps when online!

Is this a result of the certificate glitch? If so, anyone know if there is a way to figure out what apps are affected (without going offline, logging out and trying every app in turn)?

Thanks in advance...