At the birth of Mary and Johns baby, Sherlock is the last to know. Lestrade calls him after two days after he birth, asking what Sherlock thinks and Sherlocks heart just breaks because the pregnancy /was/ real and john didn't even bother to tell him she had given birth. John. His 'best friend'. He ends it and walks to Johns room and rummages around until he finds the old jumper & wooden box with 1 needle in it. He puts the jumper on for the last time and greets the needle as his last friend.