This happened to me at Prime in Las Vegas last week
I ordered a filet mignon medium-rare, and it came out medium-well, so I hemmed and hawed and finally sent it back. My friend's ribeye came out great, so I just sat there and waited. I really felt kind of awkward though since then she didn't want to eat and it got cold. Very uncomfortable situation and way too expensive not to fix. Total bill was over $300, so I wish we just sent both back, but I really didn't want to make it worse than it was. For what it's worth, I won't be going back soon...