Snap hits the upright

[Reffing Rev.]

the uprights just like the pylons are out of bounds behind the goal line.

The ball is out of bounds when it strikes anything which is out of bounds including players who are out of bounds, and pylons and goal posts.

Players are out of bounds when they are touching anything other than another player or official out of bounds. So by extension a player who is touching a pylon is out of bounds, and a receiver who runs a route, and accidentally kicks a pylon mid-stride, or brushes against a goal post on the end-line has committed a 15 yard penalty for illegal participation. (Go figure)