If it went away after some rest and drinking water, you may have just been dehydrated. If it happens again and doesnt go away with a change of activity or drinking fluids, then i'd call but otherwise i wouldnt worry too much. Maybe could bring it up to your dr at your next appt?
I went to L&D for that stomach and back pain too on Wednesday. I'm 31 weeks and turns out I was having contractions due to dehydration. It went away with the IV they hooked me up to