Drywall Hole Patched With Styrofoam

I removed a baseboard heater and installed  a outlet where the heater was wired so i had to cut a hole in the dry wall.
 But had no drywall to fill the hole, so i used some foam packaging it worked really good, jut cut a block to fill the gap and pasted it in with some dry wall paste. And painted it, It worked out pretty well.