I had my sheltie, Mickey cremated when he passed and his ashes placed in a nice little urn.  It never really crossed my mind that those ashes that I got back wouldn't be his, but I guess it could happen.  After all, my when my boyfriends parents dog died, they wanted to have her cremated too, but after a week of not hearing back from the vets office to come and pick up the dogs ashes his mom called to inquire.  Turns out there was a huge mistake - they didn't cremated the dog - just sent her to the doggy dump or did what they usually do with dogs that aren't being taken home to bury or have their ashes burned!!!  My bf's mom was so distraught & with reason!!  I couldn't imagine that happening to my pet!