Well I guess it was bound to happen sooner or later with only one set of keys. Misplaced and of course she's all closed up for the winter with the door handles and deadbolts locked as well as the hatc...
Once unlocked, one of two things: Have the locksmith who picked the lock make a key or take lock out of door, it should have a sticker with a code number, using that number either an RV dealer or a locksmith can cut you a key.