There is and has been a scam going on. It has happened to me 3 times now and I have alerted Dubizzle. I have advertised that I have found a persian. I get an email or phone call from a non english speaker telling me it is his cat. The cat was given to him by a british Family and he only had it one day before it went missing.
I am always suspicious, it is in my nature :). I wrote or told all 3 that they HAD to produce a picture, name of the vet, vet cards, age, pedigree if there was one and any other information they could give me to prove the cat was theirs. If nothing was produced they did not get the cat, well, because they wanted it to sell for up to 5,000 dhm on the street.
Since this last Persian was unchipped and unneutered I figured they would use it for either selling or mating. Anyway, this person did not call/write back, as I expected. The other 2 I threatened with the police and they didnt either.
So, my point? please ask for proof that the cat people are claiming is theirs. Most people have a picture or the former owners have a picture and for your own cat? Take a picture!!! be able to produce proof the cat is yours and hopefully less cats will be put on the open market :(
SPREAD THE WORD.