Luis Valbuena drew a walk, so he said 'see ya later' to his bat
The whole point of drawing a walk is that you don't need your bat. You just watch the balls fly by and then take your base. You could stand there empty-handed if you wanted to -- the bat is just a superfluous accessory keeping you from doing jazz hands at the plate.
Which is why, presumably, when Luis Valbuena drew a walk in the fourth inning of the Astros' 6-3 win over the Mariners on Friday night, he realized the wooden stick in his hands was unncessary and said, "See ya later, bat."