When does IE7 GET favicon.ico?

I have a web site with a /favicon.ico file. It didn't show up on IE7 despite repeated Ctrl-F5.

So I added <link rel="shortcut icon" href="/favicon.ico" /> and checked it with http://www.html-kit.com/favicon/validator/ that everything was ok. Still IE 7 didn't GET the icon file (I used Fiddler to monitor the traffic).

Then after about two weeks, out of the blue, while I was accessing a page (not the page containing the <link rel="shortcut icon" href="/favicon.ico" /> tag) on the web site, my favicon appeared!

I am at a loss. Thanks in advance.