Mine airbag light came on as well when i removed the seat and drove the car around. I had to get some water out of the car as the front drain was clogged and a bit got into the car so i ripped all the interior out+ the seat on the passenger side to make sure nothing would be damaged. I was pissed when i saw the light come on because i thought the water fried the sensor and figured that would be an expensive fix but once the seat was back in i disconnected the battery and reconnected and it was clear on the next startup.

They are quite heavy seats, id guess 50+ pounds each