Responses
Wasnt his grandpa busy with something so he couldnt go to the festival? tbh I can't remember if he ever showed up during that whole arc. it really hasnt been long after all that went down so I would guess either grandpa is still busy and hasn't noticed yet or he just started looking for Tartah and word hasnt made it to the Quifrey atelier yet

Wait did tartah leave with the brim hats???????????