Hm. I thought right away of a page where I could test that, because half of its images are in a roboted-out directory. (People were using it mainly as hotlink fodder.) Got that same "cached" blurb-- but I can't imagine what was in the cache, since my logs, downloaded immediately afterward, show that the html, css and every single image on the page were downloaded fresh.
Further investigation tells me the regular googlebot last saw the page 5 days ago, recording a 304. It picked up the stylesheet a day earlier in with-referer mode (different page in same directory). Dates on the images range from 2004 to 2007-- this is not an actively maintained page-- but it picked up all of them for good measure, including the ones it has seen within the past month.
No piwik, so it didn't get a chance to have the door slammed in its face there.
Wonder what "cached" means?
Apparently it means "If it wasn't cached before, it is now." I tried half an hour later with a different browser and different search phrase-- mildly gratifying to find myself at #2 for this one-- and the logs were silent. If I remember, I will try it again after 6 or 12 hours. If Preview works like Translate, they keep the cache sitting around for a few hours before tossing it.