The German started from the back of the grid due to yesterday's qualifying penalty, but tore through the pack to claim an unlikely third-placed finish.
When asked about Vettel's performance by Sky Sports News, Horner responded: "Unbelievable. To start in the pit lane, but not only that, he had to change wing.
"I think he had some damage on the first lap when he touched a Williams - and then behind the safety car there was more damage done to the wing.
"So to have to change that, to go to the back of the field again, and come all the way through... he just drove an unbelievable race tonight."
Kimi Raikkonen recorded his first victory since the 2009 Belgian Grand Prix.