The amulet makes a dull thunk when it hits the bottom of the trash can, and Sam feels his heart dropping with it. Dean's face is turned away, but Sam knows the way his brother sets his shoulders when he's hurting, knows the way he holds his head when he's trying not to let it out. Dean's trying to make a point, but it's cutting him just as deep as it is Sam.
When Dean steps out of the room, Sam scrambles forward and takes the necklace from the garbage, shoving it deep into his pocket, deep enough that it won't accidentally fall out. Later, he transfers it to a small rip in the lining of his duffel, which he secures with a snap he sews in while Dean is out.
After spending eighteen years in the same place around Dean's neck, the amulet has a few different homes over the next six. For a while, it lives in Sam's secret pocket. When they discover the Bunker, it moves to the drawer of his nightstand. But he brings it with him on hunts sometimes, when he needs a little reassurance.
It's in his pocket when they're standing in the abandoned church with the awful power of the trials building under his skin and Dean vowing that there's nothing he wouldn't do for Sam. It's there when he carries Dean's lifeless body into his dark bedroom in the Bunker and lays him down on the bed, tears falling down onto that beloved, too-still face. It's around his own neck, tucked away under his shirts, when the demon Dean has become raises the cruel hammer and nearly manages to bring it home. Dean doesn't know it, but it's in Sam's pocket once more when he's lying closer to dead than alive on the floor of a ramshackle cabin, gutshot and drenched in his own blood.
And now Sam's lying on the floor of the police station, black poison in his lungs and his veins and Dean's breathing it in too, but he's immune to Amara's destruction and Sam can't breathe, can barely feel Dean stroking his hair, can barely hear his words. “I'm right here. I'm not going anywhere.”
He's forgotten the amulet is in his pocket until the light starts to shine through the fabric, sunlight bright. Dean moves, draws the necklace out, and sure enough, it's glowing like a beacon. Sam looks up at his brother, too shocked to realize that the pain in his chest has receded and his hands are clean of black lines.
They both remember what Cas had said, all those years ago: that the amulet would shine in the presence of God, and sure, it's surprising as all hell. But Sam knows the stunned expression on Dean's face is less from the realization that they might just be near the Almighty and more from the sudden jolt of seeing the amulet, pulled from Sam's pocket like Excalibur from the Stone. It's a look of mingled wonder and disbelief and when Dean looks up to Sam's face, a thousand questions hovering on his lips and his heart in his huge green eyes, Sam thinks that they might just be okay in the long run. After all, even if they die today, Dean will know that the love between them was never something that could just be thrown away.
And it's enough, even now.