All I can suggest is emptying your browser cache to see if the link reappears. Are you using an older version of your browser? Which browser is it, by the way?
By the way, I found the missing .gif and uploaded it from the vBulletin folder. I have to be so dang careful about uploading buttons, because nobody likes the new vB buttons generally and I always catch hell when one of them makes it through by accident.
