1script - 7:30 pm on Dec 10, 2012 (gmt 0)
Do you mean, they are at least in the sitemap but not linked to? Otherwise how would any bot to even know they exist? I mean, Gbot pokes around with query strings and site searches and such but it may take them awhile to find the pages on their own.
As far as crawl behavior, I often see Google come pick up all pages in a simple alphabet order, thousands of them - sounds like something they've been collecting for a while from sitemaps, IBLs etc, then sorted in the simplest way possible by a URL and then came banging on the site.
That is what I call a strange behavior because it sounds like at some point in the Google system the URL and the date it's been first collected are separated from each other and that just opens up a possibility of errors in appointing the original source hence scrapers outranking the original source. The source would presumably have an older timestamp but if you don't keep your timestamps with your URLs, and then lost the reference between the two, you've lost a very important info about the URL. The whole sorting them by alphabet sounds so very basic and not Google-like. Could they not afford to keep a 10-char epoch timestamp together with the URL?
Sorry, Sarge, I might have gone on a tangent here about Gbots "behavior" in general. I can't think of a situation where a page gets completely orphaned, not even show up in the site search and the likes. I would guess they've probably already collected those pages and you've missed that initial visit. No-IBL pages must not be important enough to return to them often, so that's why you are not seeing more hits after the initial ones.