I have had a crash happen twice now, where after approximately an hour of play the game appears to be laggy, then results in a crash. Normally I will shut it down and restart it, which resolves the issue. (It wasn't near as laggy today when it crashed).
I am running an iPhone 5S. My vault has 151 dwellers, and I'm somewhere between 2/3 and 3/4 built out in all. I kill apps and restart my phone once every other day to keep memory tidy. Let me know if you have any other questions, I'm an IT Director and do a lot of bug reports so I'm happy to provide details.
I doubt there's any way to get my content back, losing rare outfits and that many caps really svcks though. I've invested about $45 into the game so far, frustrating to spend real money and lose content on app crashes!