Play at the plate

[GPC2]

To preface this post, I am a football official and know absolutely NOTHING about baseball umpiring.

I was watching the JUCO World Series this past weekend and there was a close play at the plate in the bottom half of the 9th inning. My question is about the mechanics and positioning of an umpire at home plate for a bang-bang play. The umpire was on the 3rd base/home plate baseline extended (see pic #10 at Day 7 of JUCO 2009, May 29 | Photo Gallery | GJSentinel). It appeared to me that the runner tagged the base with his left hand and the catcher either did or didn't tag the runner in the back as he was in the sitting position either at the same time, slightly before or slightly after he tagged the plate. Basically a really tough call.

It seems to me that from the umpire's view point, he wouldn't be able to see the tag on the back of the runner since the tag would have occured on the runner's back. Is there ever a time where the umpire would remain in the area behind the plate for this call?

Thanks in advance for any insight.