Well, this happened to my non-elite aunt yesterday. I've gotten her a "blue" seat a month ago online. Yesterday, my cousin called to arrange a wheelchair for her, and the phone agent noticed that she's not elite and moved her to the back. I had to make another phone call to straighten things out - she's traveling with another cousin of mine, who's elite. So, she got her original seat back being a companion to an elite.

Having said that, I'm positive that we hadn't called in the first place, she would have her seat assignment untouched.