How can I prove this?

[umpjong]

Its definitely legal..........

pg 29 rule 3-1-art.3 should cover it...
Any of the starting players may be withdrawn and re enter once, including a player who was the designated hitter, provided such player occupies the same batting position whenever he is in the line up. The pitcher is governed by Art.2 (which deals with his replacement pitching to one batter etc. nothing to do with returning to the line up.)