Swipe Tag @ 1st in the Mariners/BoSox game

[shickenbottom]

Anyone see the swipe tag call @ 1st in the Mariners - BoSox game on Sunday?
The camera angle shows a tag being applied, however, I couldn't see the positioning of the umpire to determine if he just blew it or was blocked on the play given that the throw originated at 3rd base? I know there was a runner comming in from 3rd, but the HP umps got to have some view, and why didn't the 1st base ump at least get some help or talk to someone else rather than just hold his ground. This occured 3 innings later and at least he got this one right.