Can a lien holder on a vehicle take property out of your vehicle?

Theoretically no. If the vehicle is repossessed you are supposed to be given the contents back. However, this does not apply to INSTALLED items, so if you've upgraded the stereo system, or installed premium equipment like a high-performance engine, those are considered to be part of the vehicle.

Also, it's likely to be your Word against the vendor about what was in the vehicle at the time it was repossessed.