I know,it's so annoying! Somehow,cats know when they have a Vet appointment,and HIDE where you cannot find them! You run around,calling them,and find them 3 hours later,crammed inside a box of papers in the closet...

Or,you don't find them,reschedule the appointment,and you call them once more,they come out at once,and they rub against your leg,purring..

Our kittens 'best' hiding place is up in the attic in a 'cave' of junk,where it's impossible to reach them..