You'd know about it if you did zap yourself. Sounds like a safety switch kicked in to spare you the full zap.
Feels like your arm is snap-frozen and cramped up, and your finger burns, at the same time it feels like someone has kicked you hard in the heart/chest.
Years ago I stupidly came out of the shower on a cold night and turned on the bar heater dripping wet. I ended up regaining my senses on the floor, stunned to shit house, fingers burnt, arm cramped up bad, and feeling like I just had a heart attack! I learnt my lesson quickly then.
On another note, anybody ever pissed on an electric fence?