Perhaps try to reset your phone by holding down the home button and the button on the right side together till you see the apple logo on your screen. It will not really reset anything important (data, etc will all be safe) it's more of a restart, but it restarts the whole system rather than shutting the phone down and turning it back on. Also, if the sync system in your car has a restart/reset option, also try doing that and re-connecting it to your phone.

Hi, I have the same issue. The whole plastic "belt" broke and fell off and the button along with it. I kept using it without the button though. You can still work the button, it just needs a push with a fingernail or something else small and a bit sharp (like a part of a bracelet perhaps, if she wears one on the same wrist). It's a hassle but it does the trick. My problem lies mostly with charging it cause without this whole plastic "belt" part the cable doesn't click so you have to stand there and hold it while charging - I still haven't figured a way to solve that one. Mine was out of the 1-year warranty and I also bought it in the States but live abroad, so I haven't looked into my options on a replacement to be honest.