All the work I did last night dissappeared... what happened?

This could have been a cloud saving issue. The game requires internet connection to play since it will save progress to the cloud. So it is highly likely that the game failed to connect to the servers while you were playing (which there is hardly an indication of if it fails to connect) and so when you launched the game it used the cloud version instead of the local version and just overwrote the local save with the cloud save.

This happened to me once before and wasn't happy about it :/