I know they should call the previous owner but i just thought the shelter had possibly taken it out of my hands really. I don't know whether to log into my account as i don't want to break the law as such but just don't understand why they haven't contacted me as of yet.Every time I have had to deal with a microchip company, they acted as if they were the FBI or CIA. While I was able in a couple of cases to have my name put on as a contact for friends who were hospitalized and whose pets were left with a caretaker, I don't know how easy it is to just call up and say that you are the new owner, no confirmation from the previous owner, and have them change the registration. If that worked that easily, dog and cat napping would be pretty easy. I don't know if a shelter has any further clout when it comes to something like that. Probably calling the microchip company and telling them the story is the best solution unless you don't want to disclose that ownership has been transferred. The other side to that is that if you tell them that you no longer own the cat they will probably remove you from his registration. Microchipping can be proof of ownership; I know this is getting legally complicated.
The way it works around here is that if an animal is brought into a local vet clinic as a stray, they will check for microchipping. If an owner is found they will not give the animal back to the person who brought them in but will call the owner to come and get him.