Paul Folbrecht wrote:

I do believe that it was my responsibility to hold short of 21 even
though no explicit instruction had been given ...

You are incorrect.

I'd be interested in hearing people's opinions on that
matter (the chance of some investigation).

After some initial puzzlement (e.g. "Umm, what's the problem being
reported here?"), I would hope they'd realize you need some remedial
training on airport operations.
In the meantime, have a look at AIM 4-3-18.