Rubber flange?

During my inspection today, found what looked like a “rubber flange” of some sort in the foundation. Would anybody know what this could be? The house is 6 years old, a custom build. At first I thought it was a rebar chair but the material was very supple and the texture was rubbery.

Almost looks like part of a moisture barrier.
Is that Drivid or Stucco.

Could be moisture barrier but this was a lot thicker. I going to just recommend patching the hole up.
As for the wall, I’m still trying to figure it out. The wall sounded hollow, didn’t give when pushed and there was very little space under when I was checking for the screed to pass my fingers behind the finishing. Any input would be appreciated.