Yep...just tested it. If you are in the middle of typing, close the browser on purpose. Then get back into brown cafe to that particular page or post, and the button will be at the lower left corner of wherever it was when you lost it. If you were editing, the button would be there. If you were 'quick replying' the button would be with that window....etc etc
Unfortunately, if you can't find it by now, I fear you may have lost it for good.