I did a re-inspection on a home today. The ungrounded receptacles in the kitchen had been replaced with GFCIs. When I tested one of the receptacles with a plug in tester, the tester did not light up at all (the tester worked before and after testing this receptacle). When I pushed the test button, it tripped and when I pushed the reset button it reset. I used my non-contact tester and it lit up as soon as I got it near the receptacle indicating that there was power to the receptacle.
I have never seen a GFCI trip and reset without power so unless there is something new, the receptacle did indeed have power.
Anyone have an idea what would cause this?