After Valka was taken, Stoick called for the meeting of chieftains to discuss how to finally get rid of the dragons. Too many people had already died at the claws of the dragons, and the wife of the chief being the most recent was the final straw for Stoick. Horrifically, Drago attacked, and all but Stoick died. In the chaos and fire, Stoick lost his helmet, leaving it behind while fighting for his life.
Back on Berk, Stoick used his father's old helmet as a temporary replacement, even though it was too large and ill-fitting. A few days after the tragedy, Gobber came up to Stoick and presented him with something wrapped in cloth. Within were two helmets, freshly smithed and polished to a shine. Stoick held one in each hand and stared at his friend, not reacting.
"There's one for you and one for Hiccup, when he's older," Gobber said, gesturing vaguely at Stoick's hands. "I made them from, ah…from Valka's breastplate. You need a new helmet, and I figured you'd want something to, uh, keep her close, now that she's…" He trailed off, unsure of what Stoick's reaction would be.
Stoick stared at him for a minute before slowly setting the helmets aside. He reached out and grasped his friend in a hug, startling Gobber with the uncharacteristic display of emotion. The tears in Stoick's eyes finally started to fall, a mix of gratitude and grief threatening to overcome him.