kitty mourning ritual?

Doggies have them to.
First denial.
Adjusting to a "temporary change".
Then finally realization.
The acceptance stage is when they look to you for confirmation the buddy is not returning... and you solemnly have to say no sweetie-pie he's - not coming back.

They do this in different ways.
Mine sat in his buddy's spot....... in the very spot where his buddy sat every day towards the end.. The younger sat there and looked at me intently - and the given was - "asking for confirmation" with the big brown eyes... Catching your attention and looking at you until you tell the truth. He was ready to accept it then.

Animals feel it too.