Somebody is using my storage space

As the title suggests, a travel trailer is currently occupying my storage spot; I was away traveling for two months and got quite a surprise when I went to check on things upon my return. I pay for this space, which is located in an outdoor parking area that is fenced and secured by a coded gate. I’ve mentioned it to the staff, but I haven't heard back yet.

Is it possible they sublet the spot? I doubt it, since the site is only 25% occupied. Perhaps a stranger got through the gate and spotted a space that was paid for but sitting empty for three months?

I don't mind moving to a different spot, but what would you advise me to do in a situation like this?