On May 7, 1925, Pirates shortstop Glenn Wright recorded an unassisted triple play against the Cardinals when he caught a line drive off the bat of Jim Bottomley, then proceeded to step on second to catch Jim Cooney not tagging up and then tagged Rogers Hornsby coming down the baseline from first base. Wright also went 1-for-4 with two RBIs in the game, but his efforts would prove to not be enough, as the Pirates lost, 10-9.
What was Hornsby looking at?
*shrug* I see two possibilities: the play was bang-bang and he had no chance to react appropriately; or, as you mention, he just wasn’t paying attention. It’d be interesting to see video of the play.