Searching posts by category

Hey folks,

I’m using the 2011 Theme and have hidden a category on my blog so it doesn’t pop up in the Categories menu in my sidebar.

I’d like to pull up the posts in that category by typing in the name of the category in the search form (I know there is a drop-down category list search plugin, but that defeats the purpose of keeping the category hidden!)

How can I get the search form to search by a specific category?

Many thanks!

John