mistrel If he is generally sociable and polite with other people, I really don't understand this at all. Do you have any views as to why he behaves like this with you?
What happens when you pick him up from school? Does he say hello then? What happens if you ask him if he's had a good day at school? (or, as Jess suggested, whether he'd like an ice cream ).
Forgetting where you left your keys does not mean you are “losing it”