...They may be within their rights. The property, as you stated "was theirs"
They will contest that they needed "said" property to continue with business-as-usual ~
You didnt say what your injuries were, how they came to be, whether or not Workers Comp will be involveded, whether or not it was a "Lease-to-Own" or why 'their' equipment was in 'your' truck.
If you feel the need to fight, do it in court with an attorney. Theirs is probably already in place, which means absolutely NOTHING except that they have a head-start.
Trucking companies are fairly easy to beat in court, they just dont expect the majority of their employees to fight back.
Trucking companies are very quick to take the law into their own hands, which is usually what hangs them in the end.
They operate outside the law.
I did say that they may be within their rights, which is rare, but they may have been in this situation before.
As I stated, get an attorney and find out before you do anything to retaliate... outside the law.