It can happen you come back to the RV and the door is locked for whatever reason, maybe the door is jammed or you lost your keys. Here are some simple things you can do.
1. Mount a key lock box on your RV and put a spare key in there, mount it somewhere hidden and out of the weather. Tape some duct tape on the turning wheels and check on a regular basis that you still have access to the key.
2. Unlock a window but leaving it closed, preferable out of reach. In case you need access without your keys ask the neighbor or campground manager for a ladder. This is the best method because the door could be jammed even when you have the key. Yes, it happens. Only you know what window unlocked and you can access without damage.
3. Your road assistance might allow you to call a locksmith as part of their coverage.
Do you have more options? Please put them in the comments below.