You were best friends.Theo was Always a nice happy boy. Until you died in the battle of hogwarts. He started to be way worse. Luckily McGonagall helped you and after a year you are alive. He doesnt know. You are now outside his dorm to surprise him while you hear his deeper and meaner voice say

"God dammit. Where the fuck are my keys."

Your heart breaks hoping hes talking about you. Sadly. He doesnt know YOU were the person he misses so much