Hm. I'm not able to reproduce. (Same version of Chrome but on a Mac). Could you please attach a screen shot of the partly disappeared box? Thank you.
I can reproduce this on Ubuntu in Firefox and in Chrome. Search ctrl-f5 type "param" – or anything to get focus on the TOC Hit esc – search disappears Hit esc again – TOC dissapears. Alternatively you can tab until one of the TOC links has focus, and then hit esc.
Got it now, thanks :)
We should consider making this into a feature, sometimes the floating TOC covers page content. If we had proper buttons and a visual indication of controls it could be useful rather than a weird surprise.