Please look under Pet Psychics, chris has recommended a really good genuine Pet Psychic who could really help you.
Muffin is a beautiful boy very proud and serious?
I do hope you have some good news I could be wrong but I feel Muffin just wanted a taste of freedom to explore as cats do, having had cats myself I know if they are injured in any way they will find a place to hide to gain strength to then start on their way home if they can get themselves home from any injury they will.
My cat was attacked by a dog, she had a puncture wound to her belly, she went missing for days I used to be out day and night with the kids calling for her and looking for her, door knocks, posters, the works.
I used to leave my bedroom window open it was low to the ground just enough for her to jump in and out and one night she did just that she came home
I thought she was alright until I saw the lump on her belly so I took her to the vet and he had to keep her in as the puncture wound from the dog did damage to her insides but she was fine after that.
I do hope its good news and you have him home soon