> Is there something, somewhere in one document or one page that explains how it actually works?

Sorry, no. It is so complicated that Inyo can't train all the clerks in all the situations. So you get different answers every time you ask a different person. Also, there are so many different combinations (day hike, overnight, Trail crest exit, other trails, etc. etc) that both your questions and the answers people give are not usually understood perfectly. You could be asking about one type of permit, but the person answering mistakes it for another, so gives you answers that are off base.

That 24-hour rule is for people exiting to pick up supplies and then get back on the trail -- usually PCT hikers.

> "Why didn't you just call ahead, we always have some cancellations, and could have held them for you?"
That's bogus. Whoever gave you that remark did not understand your question or situation. Their answer applies to reserved permits. If you show up AFTER the deadline to pick up reserved permits they give them away to the walk-in people, since you were a "no-show". And so, if you had reserved permits, you could have called in and asked them to hold them for you.

Edit: To top it off, this year the system went to a new online lottery and the permit process in the V.C. changed as well. So what we knew last year has changed.