Yep, I'm between a rock and a hard place with this situation. I'll never find the beak without breaking the membrane. Uhhh! I've been doing this for my many years but this is definitely a first.
If its positioned correctly, and against the membrane, maybe you can feel it with your fingertip? I had trouble finding one that had half-way zipped and stalled, but the beak was so firm, I felt it without actually seeing it.
This is my first year with broodies, but I had 10 I think, and never saw such a thing, so I feel for ya!