I wanted a shot of the hole. I couldn't see the hole! I scraped around with a small stick. I probed with a sharp-tipped pine needle that had to be thinner than Mamma's snout. Nothing!

Here's my theory: Mamma brentid plugged the hole with some fast-hardening excretia to keep predators away from her egg (or eggs?)

I had had presence of mind enough to mark the location of the hole at the apex of converging pencil lines while Mamma was still gnawing away. No brentid was going to foil me ;-)