2005 Ford Focus ZX4- Passenger air bag turns off with ADULT sitting in seat. Light on dashboard but gone now?

2005 Ford Focus ZX4 w/ 131,000 miles. There is a light just below the hazard lights button and above my radio that notifies the driver when the passenger's air bag if off. It usually only lights up when I have my backpack on the seat but recently when my 160lbs boyfriend sits on the seat, the light comes on that it's turned his air bag off! When you turn the car off and then on again, the light vanishes and doesn't return for the duration on the trip. However, two days ago I noticed that instead of the 'passenger’s airbag off' light above my radio, on my actual dashboard (next to my oil temperature gage) the check airbag light was on. It stayed on for about a day and a half and it didn't matter how many times the car was turned off and on, it stayed on. As of yesterday afternoon, the light is now off and neither light is coming on anymore. I have a feeling it's the front passengers airbag sensor in the actual seat but anyone know why it keeps going on and off? Will Ford be able to pull a code if the check airbag light isn't lit on my dashboard? Thank you!!!