While they’re busy loading your bike, hop into their driver’s seat. If you’re lucky, maybe they left the keys in the ignition, free car! If not, either surprise the fuck out of them and ask “Where are we going?”, or call the law, or just beat the shit out of them, your choice.
Alternate idea: Lay down in the back seat, and once they get going, call emergency services and say “Help, I’ve been kidnapped!”, and try to describe their vehicle.
How do they know how the hell you got in their car? And stick with it too, you know that thief is gonna be shitting bricks and trying to get you to shut up and get out of their car or something, go ahead and let 911 hear their bullshit.
Note: If there’s even the slightest chance there are any cameras around, you probably shouldn’t do that, it’ll catch up with you…