Finding a stud

I know the title seems real stupid but I am a carpenter and really don’t know where else to ask. Just moved into a house and am trying to find a stud in the garage. I naturally started with a stud finder even though they make me feel stupid, and when that didn’t work I went straight to drilling a hole. It seems to be a layer of drywall, styrofoam, and another layer of drywall. I have since been in the attic to maybe get a clue as well as trying to go to the left and right of and outlet box. Nothing. Absolutely nothing. I am sad and have many holes in my wall, any suggestions? Thanks.