Well, well, well.

Took the mower deck off this evening; there's nothing like looking if you want to find something.

The "nail" (blade spindle) I was told was destroyed and irreplaceable appears sound.
Fingers crossed that I can get at it further tomorrow.

If it's what I think it is - the radial ball bearing - it's a $20 part, and I believe it's easy to get.
The tool (and muscles) to do it however might be a bit more.