Thank you, Vanessafox. I haven't gotten very in depth with my use of Webmaster Tools, so I didn't know those options were available.
Today I added more "gravitas" to a product (ecommerce product) page that had been hit hard, dropping from #6 to #84. A few hours later I received three orders for these $1000+ widgets. One order every day is very good for me, three in a day is very unusual, but three in two hours is something I've never seen before.
In looking at the log files, I saw that all three visits came from Google, using either "Acme widgets" or "Acme model XYZ" as the search phrase.
I don't see the page ranking anywhere for those results until I get to page 9, and I doubt very much that Google would turn things around that quickly. It's either an odd coincidence, or there's something else going on (perhaps a mention on a forum).