It probaby wasnt a Yellow Belly. The petco snakes (or balls atleast are CH...Where they buy em in bulk)

Did it have a CLEAR belly? Insane flames? Faded head spot?

Most peolpe think a yellow bellies actual belly is yellow, its not. Its called "yellow belly" because of the yellow on the sides...where you can SEE a deffinent color change between the yellow and tan/brown on the sides.