His last play was around 9min left in the 4th quarter. I just looked at the play by play on nfl.com I'll have to watch it when I get home.
Just saying, Ivory has a history of tweaking things and being out a game or two. It's probably the main reason the team won't feature him. His violence in running also leads to injuries.
I just re-watched his last two carries. The run before his last one looks like he may have gotten his right ankle caught between two players on the way to the ground, but he did stay in for the next play and was able to still run hard.
The camera doesn't follow him off the field, so there's no way to tell anything more.