I was not expecting there to be direct conflict between Sam and Shagrat. I was wrong. After dispatching the crawling Gorbag, Shagrat howls in victory and lurches toward the door where Sam is hiding. Unable to think of doing anything else, Sam jumps in front of Shagrat, and Sting blinds him. There’s also something about the ring providing Sam with some power, as I had thought before.
Shagrat holds back, but slugs Sam with his bundle when he lunges forward. Shagrat takes the opportunity to fly down the stairs, while Sam tries to follow. Partway down, Sam realizes that he has another choice: catch Shagrat before he can send for help, or try to find Frodo before Snaga does something horrible to him. He chooses Frodo, and heads back up to continue climbing the tallest tower.
As such, Shagrat escapes, and the mithril coat begins its journey to the Black Gate.
In an alternate universe, Sam catches Shagrat after a chase, but doesn’t have the stomach to outright slaughter him. The two somehow forge a cautious friendship, and work their way across Mordor. Partially unaware of the worth of their treasures (the mithril and the ring), they wander to Bree and open a new pub, the Ringed Armorer. Somehow, Sauron never conquers Middle-earth. The pub is modestly successful.
But, yeah. You can’t blame Sam for picking Frodo. Although, he doesn’t even know that he’s still alive. I guess it’s a gamble either way. He knows that he might not catch up to Shagrat, or be killed by him, and just as much, Frodo might not be alive. You have to live with the choice that you’d rather have if it all worked out okay.
Days Until The Hobbit: The Desolation of Smaug: 1
“He came to the guttering torch, fixed above a door on his left that faced a window-slit looking out westward:…”