In ACOK, Arya's false argument that convinced Gendry to run with her was that, once that he's commanding Harrenhall, Vargo Hoat will cut one leg from all of the servants, the left one.
In AFFC, when Jaime gets to Harrenhall, one of Gregors man says that the cook opened the gates for them as a revenge to Hoat for choping of his left leg. The cook is also shown walking funny in the same chapter. So the"Kid" was right after all.