A question about Pigwidgeon.

[tacrader at yahoo.com]

No: HPFGUIDX 13555

I have searched this site and have yet to find the answer to my 
question, so here goes:

At the end of PoA Sirius sends a letter to Harry with a P.S. that Ron 
might like to keep the small owl since it was his (Sirius) fault that 
Ron had lost his rat.

Why then does Harry act like he has no idea who Pig is in the 
beginning of GoF? After Ron explains who Pig is, Harry asks about 
Crookshanks. Why wouldn't he have asked about Pig, knowing that his 
godfather had given it as a present to his best friend?

I must have missed something, but I cannot for the life of me figure 
out what it is!

Thanks!