[SOLVED] Mobile dropdown nav menu appearing in non-mobile view header

I've just been through an exercise of changing the hard coded CSS and similar defaults for the Montezuma theme. I've done this so that if (? when!) something I've tried not only didn't work but didn't work so badly that I want to wipe it out and pretend it never happened, I can 'reset all'. Previously, if I DID hit 'reset all' I'd then have to go back and reinstate all the GOOD things I'd done to tweak it to my requirements.

It has NEARLY worked. Now, when I hit 'reset all' it goes back to my last 'good' settings ... EXCEPT ... a drop down navigation link has appeared in the site's header area. As far as I can work out it's the navigation that SHOULD be shown as an alternative to the pretty icons if viewing the site from a mobile device. But I can't find any code in my non-mobile header that would make it appear ... and I'm pretty sure it's never appeared before when I've 'reset all' (then regretted it!)

I'm sure that if I played around I could just delete it somehow, or set it via CSS so that whilst it is there it isn't actually visible (it doesn't affect the actual layout - it shows up in an area that would otherwise be whitespace). However, the site I'm working on may well be visited on mobiles. I don't want to do anything that would disable or hinder their access.

You can see the culprit at http://disc-over.me/about/ Can anyone tell me how / why it's there? And more importantly, the PROPER way to get rid of it?

Any help or advice (or even just sympathy! ) gratefully received.