Dollar and Thrifty have a desk in the TPA terminal and are manned 24 hours.
Not a Dollar or Thrifty issue, but one for car rentals in general. Since your flight is arriving close to midnight, technically you are picking up the car the next day in the early a.m. We had an issue once years ago where the rental agent could not pull up our res since it was for the previous day, luckily there was another agent there who could override it. Not sure how the rental computers are now or if it was just a problem with their system at the time, but safer to book for just after midnight to avoid a possible delay in getting you car. I know car rentals operate on a 24 hour clock, but at the time their computer seemed to purge the calendar day at midnight and had us as a no show even though we were just 20 minutes off the plane. Would hope that technical glitch is one they fixed, but ya never know.