A lot of people are experiencing this issue, and I believe there's no way to restore your vault, as the crash happens due to corrupt save file (it becomes 0kb). The only way to play the game again is to reinstall it and start over. But the crashes will still be happening. I was in the same situation as you, and was very frustrated at first... Lost two vaults to these crashes. But there is a solution! =)
Right now I'm using an app to backup the saves, and whenever the game gets corrupted - I simply restore the previous backup. Here's the app: https://play.google.com/store/apps/details?id=net.fosrollback.fosrollback
Just make a backup EACH TIME BEFORE you start the game (don't rely on auto-backup, it's crap). This way if it gets bugged, you will be able to restore it from the closest point. And try to stick to short sessions, the longer you play non-stop - the more chance that it will get bugged.
And don't worry about losing that stuff you had in the old vault. In a few days it will seem unimportant, it will all come back quickly, and much more. Actually there's a bonus to this app (some advice on tactics from my personal experience, don't read further if you prefer learning everything yourself, and making your own mistakes=)). If you wish, you can backup the save before you open a lunchbox, and if it gives you crappy stuff - just restore and open it again=) Repeat untill it gives you some legendary weapon, like Fat Boy, then equip a dweller with it and send him out, packed with as much stimpaks and radaways as possible. He will bring you so much loot, that you will have to build more storages to keep it all=)
Also make sure to keep your dwellers count under 30 (29 idealy), until you gather enough loot, level them up and equip them with good enough weapons. Because when you reach 30 dwellers - the molerats will start digging their way into your rooms, and you'd better be ready for them... And don't build the radio-station, untill you want to grow the population over 29 dwellers.