Its not just GM, allot if not all cars cam sensors are oil pressure driven. My guess running it without any oil damaged the sensor. When you take it to the dealer I would not mention you starting the car without oil as this part is covered by the 5year/100K powertrain warranty which doesn't cover issues caused by improper maintenance(yes that's what I would call running an engine without oil even for a short period).I can't believe that gm would engineer an engine that would be that sensitive to running without oil from an oil change for a minute or so.
The fact the code comes back after you clear it indicates there is a problem with the cam timing or the sensor it self. Since you indicate the car is running fine, I would think its just the sensor. Is out motor interference engine? if the timing was off and it is, you would probably be hearing some not so nice sounds as the valves make contact with the pistons.