There was another thread on this topic. Mine will also sometimes not find device. Also, sometimes will be playing one minute and then music quits and message "device not found". Sometimes will start up again say in 20 to 30 minutes.
It's a long shot, but maybe make sure the firmware on your device is up to date. If it's older, it might not have what it need to properly connect. Apple stuff checks for updates automatically, but you should be able to see what version you're running and compare it to the website to see if it's the latest.