Was it your fault? Did you do something wrong? You spend hours analyzing everything: every word you ever spoke to him, ever look you ever gave him, every action you ever preformed in his company. How do you determine which action did it, which action gave him reason to dump you and never return?
At least Aunt Lavinia never found out. She never even asked why you were gone so long. Maybe she didn't even notice. It wouldn't be the first time. Nor will it be the last. Maybe it would be better if she did. Then you would have a focal point for your anger, an outlet for all the fury and bile you would pile on him, if he came back.
If he came back. First of all, you'd spend a good hour chewing him out. How could he just leave you like that? Aberdeen instead of Croydon, to boot! And going back to Gallifrey without you. He got to go back home, and you got stuck in the middle of nowhere. You had to call UNIT—collect, mind you—and wait for a ride back. Not to mention the half dozen times you reached for something and realized you'd left it on the TARDIS.
Then, after running out of words that would make Lavinia pretend to faint, you would wrap your arms around him and refuse to let go. You'd ask for a scarf just like his, that crazy, mad fashion insult, and never say another word about it again. You'd say whatever he wanted, just as long he let you back In the TARDIS.
Maybe later, after you'd marathoned your way across a few more planets, then you'd ask why he took so long to come back. But whatever he said wouldn't be half as important as the fact that he was saying it to you, the fact that you could hear him.
He'll come back.
He has to.