A lot of our motorhomes don't have "master keys", but instead, they use a "common" salesman's key. You should have a deadbolt which will not have a "master", and will secure the door. If all you're doing is locking using a Trimark lock, then you more than likely will be susceptible to someone else being able to gain entry. To check for yourself, just look for the number on the key and Google it. A lot of Trimark locks use the "CH751", "1099" and "2099" as common keys that will open doors and basement bays (they are even more susceptible to using common keys). On the other hand, if you have a deadbolt, such as a Schlage, then that will be the lock to use when you're away.
Dewey & Sharon
Southern Maryland suburbs of DC
2015 Tiffin Allegro Bus 45LP