I don't see the Commonwealth Attorney advising anybody other than law enforcement for something like this. You can bring a suit for dentinue in general district court and get it back....if he has no legal claim it should be straight forward and pretty easy. Meanwhile if he has no legal claim the sheriff ought to be able to help you bring a charge for larceny and entering property to interfere with property rights. If the trailer is worth less than $1000 you can go straight to the magistrate and swear out misdemeanors yourself. If the sheriff is saying he won't get involved because it's civil, that means the other guy has articulated or documented a legal claim that has convinced him to stay out, and will be a bad look for you to go around law enforcement on a self help mission.
Really good advice. The sheriff doesn't have the authority to settle competing claims. A judge or Justice of the peace will listen to both sides and make a decision. Going to someone else's property to settle an ownership of movable property dispute will cause grief, probably for you. You have a legal avenue. It is called a civil action. With a court order the sheriff will go get the trailer.
