Scammers take advantage of people who have lost pets and posted fliers or notices on line. They will be more than happy to return your pet to you for just enough money to cover the shipping costs. Sometimes you will even get a call purportedly from a legitimate shipping company to confirm the details. Unfortunately, scammers take advantage of people who have lost their pets by contacting them and promising to return their pets to them although they have no connection to the pet.
If you are contacted by someone who says that they have found your pet, ask them to send a picture and make sure it is not the same picture that you may have posted on your flier. You can tell them that you merely want to confirm that it is your pet that they have.