There are 3 short stories featuring Bigfoot and they are set in the Dresdenverse between various Dresden Files novels, and featured in three different Short story collections.
"B is for Bigfoot" by Jim Butcher in Under
My Hat: Tales from the Cauldron
"I Was A Teenage Bigfoot" by Jim Butcher in
Blood Lite 3: Aftertaste
"Bigfoot on Campus" by Jim Butcher in
Hex Appeal