PoA question and Sirius

[kermit13166 <kermit13166@yahoo.com>]

No: HPFGUIDX 50372

I have a question that is bugging me that perhaps someone can help me 
with. In PoA, Sirius tells Harry that he was the one who sent the 
Firebolt....10 yrs worth of gifts etc... My question is two 
fold...One-how did he get to Gringotts to get his money out without 
being seen and second Sirius said he gave Crookshanks the 
order....Would no one find it odd that a cat delivers such an order? 
Just wondering....