When using a storage unit space yes when you pull out and leave small things behind everyone thinks you left it. they don't know if you are still using the space. Right or wrong to take well simply out they DO.
Most of us have found that when using an open air storage space for an RV to prevent this and so you CAN leave the stuff you want when using your RV, is to buy 12 small cones. They are very inexpensive.
Place 4 on each side and 2 across the front and back of your space when you leave. This lets EVERYONE know you are still paying for that spot and using it and it will actually PREVENT the theft of things left on the space. And/or finding another RV parked in your space when you return. Been there seen that too.
These same cones come out at CG sites when I leave for the day also. IMHO cones are a must have to have on board at all times.