Ball pythons are very shy and secretive animals often not leaving hiding places for weeks. If your ball python is hiding, it means it is happy. If he was wandering around or laying out you should be concerned. Cruising around at night is normal since they are nocturnal.
If your snake is in shed it will be more inactive. Shedding is a sensitive process and they are very vulnerable during it.
Thermostats are hard to find in pet stores. Your best bet is to order one online. The reptitemp 500r is a good thermostat for single setups. If you want to get a temporary dimmer, home depot and lowes sell a piggy back dimmer that you can just plug your UTH into and then plug it into the wall. Test it out on a light first to make sure you are dimming in the right direction. Also, make sure you have your thermometer probe right on the glass where the UTH is under the substrate so you know the hottest point the snake can reach.