I had the same issue with Moodle 2.2. The settings block is very tricky. It can be set to display only on one page, or on all pages, or the home page, etc. First step, find the settings block in one of the classes or homepage, (whereever it isn't hidden). If it's hidden everywhere, maybe create a new class so it will be displayed (just a thought)? Once you find it, try fooling with the alignment, right, left, and the weight, -9, 0, + 9 to see if that makes it become visible. If not, if your theme allows, flood the page with other blocks and in the process of the blocks getting displayed, you may discover your settings block. It's there in the background, it's just hidden and inaccessible, Lord knows why this is allowable, please fix. You just have to move everything and its mother around to try to sneak a peak and see the settings block to make it visibile once more.
Ayyyeeee!