Keep 2 needles threaded with black and white thread in your bedroom or bathroom. You can stick the needles into a bit of sponge or cork. Then when a button pops off you can sew it on quickly!
I keep a needle in the credit card section of my purse. When I get a run in my pantyhose, I pluck a strand of hair and use it to catch the run. The hair is about the same color and it looks almost invisible. A hair is a good temporary fix for a hem or even a button in a pinch! Laugh now. Thank me later!