This problem has happened before quite a few times. In each case the outcome was fraught with difficulty. I believe that I know the legal answer and therefore the correct answer but cat rescue organisations don’t always follow good legal argument. They do what they like.
Sometimes a cat who is owned by somebody ends up in a shelter. Someone other than the owner adopts the cat from the shelter and takes him home. Then the original owner discovers what has happened and wants their cat back.
This scenario can happen quite easily when a cat becomes lost for a while and then is found by a neighbour who takes the cat to a shelter. The cat has no identification so the shelter finds a new home for the cat and along comes somebody else other than the owner who adopts the cat. Subsequently the owner discovers what has gone on and the dispute on ownership begins.
Uncooperative animal shelters
In the two or three instances I have read about this scenario on the Internet, the cat rescue organisations refused to help in ensuring that the cat was reunited with the true owner. In some instances they have been deliberately obstructive by not informing the original owner the name of the new caretaker. Their argument is that they are under an obligation of non-disclosure. This makes it all but impossible for the original owner to sue for the return of their cat because you have to know the name and address of the person who has your cat.
The legal position, as far as I am concerned, is clear. If a domestic cat does end up in a home as described above then the original owner has a clear legal claim upon the cat to be returned. This is because there’s been no legal transference of ownership. There is nothing in the history of the cat which tells the court that the owner willingly and expressly transferred ownership of that cat to somebody else. Therefore ownership must remain with the original person who possessed the cat.
On Quora.com there is a similar story and the title to this article comes from that story. Michael Kingsbury took in a stray cat. Before he decided to adopt the cat he checked with the local animal shelter to see if anybody had reported a cat missing and he checked whether lost cat flyers had been posted in the area. He couldn’t find an owner so he kept the cat. The cat settled in just fine. After three years she disappeared.
Apparently she had become stuck up a tree and a neighbour had got her down and taken her back to Kingsbury who decided not to let the cat go outside anymore. A few days later he received a call from a woman who had seen his lost cat poster and she said that the cat was hers. He said not anymore. The woman who claimed the cat did not become hostile but she made a good argument that the cat was hers because it transpired that Kingsbury had adopted a cat three years ago who belonged to somebody else, namely this woman.
Legally, the cat was still hers but she waived her rights because her husband was on the side of Kingsbury. This was nice of him and his wife. Kingsbury and the lady became friends which was nice too. The cat lived to 20-years-of-age.
Cat changes home voluntarily
All arguments about cat ownership are the same as those concerning any possession such as a watch or car. The complication with cats is that they are living creatures and they have a mind of their own if they are allowed outside. From the cat’s perspective they don’t consider themselves owned by anyone which is why they sometimes change homes voluntarily and of their own accord. When that happens the legal owner is still the legal owner but they have a weak argument and it proves that cats are not truly owned by humans. This muddies the argument on legal ownership.