I'm assuming that these wires have some form of molex connector that comes out or is near the seat space (Otherwise they would be running elsewhere )
chances are (at least my guess) is that the wires are for either the passenger seat airbag system as you suggest, or for a heated and/or power seat option. most modern cars are all done the same until the final options phase. normal/heated/power seats; power windows/locks etc. The wiring should be all there.
You would probably be better off running a dedicated fused line to your electrical system since you mentioned they were a smaller awg. wire. Besides, there might not even be a live connection in your fuse block for these missing options. Take a look there for any missing fuses labeled passenger SRS (Supplimental Restraint System) or seats, windows etc.
You might also try cross-referencing the molex connector with some online or dealership OEM seat upgrades if you can find them. This way you can see better if the heated/power seat plug on the upgraded seats look like they might fit the plug that you have. That would identify it immediately.