I've had that exact thing happen to me, when I was switching a live program about a year ago.
It's the most unnerving thing you can imagine. You're just going along, then you suddenly realize you're disoriented. You don't know what it is, just that something's ........ wrong.
When it happened to me I thought it was another ocular (sight) migraine. But no, in addition to not being able to see, I was unable to speak coherent sentences. The words were coming out, just not the right words, and not even in the right order. I knew what I was saying, I just couldn't make myself say the right word when I wanted to.
Within five minutes, I was completely normal.
The next day at the doctor, he diagnosed it as a migraine unlike any I'd had so far. No pain, just complete and total disorientation.
Until I knew what happened, it was beyond scary. I really thought I was having a stroke.
Thank goodness, it has not happened since.