I took apart a controller out of curiosity. I don’t even see the foam bit that you guys are talking about.
It's between the circuit board and the white plastic backing for the buttons. Right below the 1234 lights. The ribbon cable thing for the buttons loops over the top of the white plastic and the foam is behind the ribbon.
Possible you're not seeing it because your working with an older model controller. I believe it was the first generation sixaxis and some early Dualshock 3s that don't have the foam piece and instead, have the ribbon cable actually plugging into the circuit board, rather than simply being pressed against it via the foam.
