It's happened to me on occasion, I've set tasks, then decided to play about with some designing, got the Bart screen and then gone back in, or just clicked a back or home button instead of exiting and end up with people who are free when I was sure I'd tasked them, so now I sometimes just click the friend button then come back to force a synchronising before I do any editing or leave....
As for things like trash, money and doughnuts, my assumption is the 'counters' information is held locally on the device and then just update the server next time around whilst it's the server that remembers all the other stuff and just reverts that and accepts the local data on the 'counters'