Concrete is a semiconductor and wet concrete is a pretty good conductor. See if you can light a 7-1/2W bulb that's hooked up between the hot line and the floor. If that works, try a 100W bulb.
Since you're not dead I guess the current flow, 120v through concrete resistance through skin resistance through body resistance and back through skin resistance was less than 20 mA or so. 10 mA is painful and 1 mA is a tingle.
I had one probe under a wire nut then the other one dropped to the floor and my meter started beeping. Maybe I will do some experimenting.