Hi goosing, I'm so very,very sorry to learn of the loss of your dearly, much loved cat, I have been in the same situation twice this year although 1 of my cats died of old age my other puss "Merlin" was tragically taken from us back in May, my remaining cat did look for him as they always played together, I eventually got 2 kittens ( brother & sister ) who get really well with" Millie" and have formed a close bond, it also helped to ease myself & my husband pain of losing two, much loved and valued members of the family.
I know it's too soon for you to consider but maybe in time you could introduce a new pal for your remaining puss, in the mean time all I can say is just give your cat loads of affection and your self time to grieve.
It's been 5 months since we lost "MERILN" and 8 months since "SOOTY" passed away but we still miss them both and will always love and remember them for as long as we live.
With my deepest sympathies to you and your family.
Love from cat woman X X X :-(