I am looking for a plug under the carpet I know it is covered with a brass plate. I bought a $20 stud finder that warns of electrical wiring, but have had no luck. I've poked. Scanned and even hammered. I don't want to buy a metel detector for this one little project. Are there other methods? Oh I need to mention that the carpet is on a concrete slab. Thanks in advance for your help.

You can get a device that picks up the "induction" from magnetism that is the basis of electricity generation. It looks like a thick pen. It usually is turned on from a button in its base or side. Electrician uses this to determine if a wire is either live or dead. It cannot say what voltage or how much voltage is present. It just gives an audible, visual or both signal when it picks this induction from a live circuit. The only issue that you might find with this is the brass plate might mask the induction from the detector. Also, the receptacle HAS to be energized as well, obviously because the detector won't pick up a signal that has no "induction" in it. It might be worth a try and if anything, it is a nice tool to have for future projects.

I would Make a little device with 2 needles, a battery and a buzzer or light, then as you push pins through carpet, when it makes contact with brass plate it will buzz or light.
Maybe attach the pins to a small broom handle, then start poking around.
If this box was done with conduit, with circuit off, push fish tape and listen for location.

Thanks, Ill try that