New Illegal Substitution Rule

[ljudge]

Gee, I'm on a roll here. I'll preface this one with I do NOT have my 2005 rules book just yet. But something else in the football guide to consider...

1st and 10 for A on it's own 10 yardline. Prior to the snap B11 counts the defense and incorrectly thinking he's the12th player, runs off to B's sideline at A's 20 yardline. The same player then realizes his team is a player short and runs back onto the field.

This is ruled as a dead-ball illegal substitution foul. Why? He's still a player by rule and there's nothing to say he can't leave the field and return. He was never replaced and therefore never changed his status from player to something else. But again, I don't have my 2005 book so perhaps something changed that I wasn't aware of. The 9-yard marks thing I thought applied to A only.