Well, I got to Vault 112 (with Charon and Dogmeat) and got Dad back out. After our conversation, I get a message that Dogmeat went home. I forgot to "re-grab" Charon before leaving with Dad, though, on our way to Rivet City.

Well, along out journey, we come upon RobCO and in the parking lot, I notice a little skirmish going on. Dad, being the heroic guy he is jumps into the fray. As I get closer I notice they are Talon Mercs. I wonder who the sorry sod is that they are attacking.

As I take aim, a dog comes into view. DOGMEAT!!! Awesome! So we dispatch the mercs and I am able to grab Dogmeat and off the three of us go.

I wondered as we moved on if Dogmeat actually triggered the mercs. I guess he must have since I found no other "bodies" after the fight

I doubt if Dogmeat triggered the encounter, those won't happen unless you are in the area. It was most likely that after your presence made the Talons appear, Dogmeat just happened to be the nearest enemy, and the Talons focused on him instead of you.

Good point. I had more than likely "caught up" to Dogmeat on his journey

Hmm, this must mean the Followers still walk across the map when you send them home in this game. They initially did this in New Vegas, but changed it. I thought they also did this in FO3.

It would explain why it can take game days for a follower to get home.

This happened to me on another character with Dogmeat. I asked Dogmeat to go home when it was time for me to play "whack-a-mole" for Moira. He slowly walked away with his head hung low...

Dogmeat was stuck at the Farragut Metro Station with a crapload (3 or 4) of deathclaws, an Outcast patrol, the raiders in the area, a talon merc squad, and the super mutants across the river. I had waited for him to come home for at least a week and then console commanded myself to his location. What a surprise that was!

I am using the unofficial patch, so maybe that changed things back?

Yep, Fallout 3 and Skyrim followers walk across the map back home. In New Vegas, they fade out and vanish to return home.

I remember losing Fawkes after telling him to go home but wanted to recruit him again, he was not at the library even after many in game days.