Rachel, yours has come closest to an answer, but sadly not a complete one.
I can understand that the vascular nature of the area my make it prone to shrinkage. But this is more, much more. The button mushroom that is left after a ride seems to have somehow become tortoise like and burrowed within.
A warm shower doesn’t just grow it. There comes a point where it pops back out.
So, something was there, and not just deflated and cold blood vessels. And something popped out.
Where did it pop out from?
The wife really wants to know in case she needs to go digging with a warm tea spoon one day.