My touchpad broke and I couldnt download the touchpad driver to fix it on the spot because there was no way to get to the download button with tab and enter, you had to click it.
In your situation, a couple possible solutions come to mind. 1) turn on "mouse keys" which lets you use the numpad to move the mouse and click, 2) a vim addon for the browser (e.g. vimperator or tridactyl) likely could've clicked the button via the hints mode. It's in the past now so maybe these wouldn't have worked or you didn't know, of course, just fun to think of what I would've done.