Controller reported airport management failed to respond in response to a non-communicating vehicle entered the active runway; which disrupted landing traffic.

Narrative

I was working Local Control during this incident. Traffic was steady moderate with multiple aircraft in the pattern to include a Piper Cub that was not transponder equipped along with multiple arrivals & departures.I cleared a P28A Cherokee for their practice approach to runway XXR.About a minute later; a pilot reported seeing a vehicle on runway XXR.It wasn't there when I had cleared the aircraft for their landing to that runway; because I had scanned the runway as I was clearing them.I don't know which aircraft reported seeing the vehicle because they didn't use a callsign (different issue). But as soon as it was said; both the Ground Controller (GC) and I scanned XXR and immediately saw a car *ON* XXR that was stopped at intersection 1 . At that point; I told the short final Cherokee to 'go around right side.'It was just the Ground Controller (who was also the CIC) and myself. I told GC to see if any FBO vehicles were on the freqs. None were on Ground's; nor on mine. I then told GC to call the FBO via landline; and tellandlines; send someone for an immediate response to someone parking a car on XXR.While using binoculars; I observed the driver of the vehicle exit and walk westbound onto taxiway 2 turn around and it appeared that he was taking pictures of his car with his phone. Both of his arms were held out in front of him and he was facing eastbound towards his vehicle. After he was done; he walked back to the vehicle; got in turned around on the runway and exited at hotel onto taxiway 3. He then drove north on 3 to the intersection of 4; where he did a few 360's; then he headed east on 4 where we lost visual contact with them and they did not reappear.About a minute later; the FBO called ground responding to the incident. A solid 3-4 minutes; possibly 5 minutes; had passed from the time we made the phone call. They could not find the offender.Recommendation: If the FBO (Airport Management ) numerous fuel trucks and airport vehicles were monitoring the frequencies of either Ground or Local Control; they did not respond to any of the calls. It appeared that the FBO downplayed the urgency of the response needed for a civilian vehicle PARKED on an active runway.If their response had been quicker; the situation might have been resolved instead of dismissed.