Gabriel is with Team Free Will(Sam, Dean, and Cas) to explore an abandoned building. It's not related to the main events happening, but they decided it was worth checking out because there were some haywire signals coming from it.

While the other three were actively LOOKING, Gabriel was kind of just strolling along with them, mostly uninterested in the search. He was just there because he had nothing better to do.

That was, of course, until they stumbled upon you. An archangel. Injured, and just laying there, almost curled in on yourself, on the ground. Your wings are torn and bloody, and you're mostly hidden under them. They can't even tell if you're unconscious or not.