It's possible, I came back from a seemingly crushing defeat, in silver.

Yep! The game was massively behind, and we fucked up hardcore early game when I invaded the Hecarim and had a level 2 teamfight break out (which Vayne hardcore carried with her "weak early game"), and the game was not going well, but I ganked a lot, got fed myself, and got others fed, and we came back despite having an open nexus! So, it's possible to come back from games, even in silver. Don't just FF if the beginning is bad. :P

http://i.imgur.com/TtjcKmc.png

At one point, it was like 29 to 50 something. But we got our act together, played like a team, and they focused the hell out of me which made it easy for my team to come through. :P

Also restored my faith in the people I queue with a bit.