Searching my Posts for Tags?

I’m trying to locate an old post on my WordPress blog by looking for one of the post’s tags. (Luckily I’ve been very good about tagging each post.) When I’m in the Posts pane of the WordPress admin, I type the tag into the Search text box. But I get no hits, even for tags that are clearly there on many posts.

Does the Admin’s search box not search for tags?? If not, how can I search my posts by tag?

Thanks for any help.