Air bag light and seat

[Laurence]

I have installed a DVD system over the weekend and for part of the install I had to remove the passenger seat.
While the seat was out, I had to move the car.

Since putting the car back together the air bag light is on.
I'm hoping that this is only because the seat was disconnected and removed - I'm assuming that there is an air bag in the seat or that air bag sensor also monitors the seatbelt pre-tensioners which.

Can anyone confirm if I am correct.
I'd like to take the car to the dealer to get it reset, but I'd rather tell them why it came on so that they'll just reset it.