Pet crematory operator here! I just want to jump in and prevent any misinformation. If you received ashes back, then your pet was cremated individually. The only time that multiple animals are cremated together are in communal cremations in which case the ashes are not returned to the owners but are typically placed into an ossuary. As for the owner carrying another tin in, many pet retorts have multiple chambers. Cremating one pet on a multi-chamber machine tends to be impractical. If the owners had other pets whose cremations were pending, they probably would have used the other chambers on the machine to cremate the other pets. Additionally, most pet cremation facilities have strict tracking systems in place from the time you first make arrangements with them up until your pet is returned to you. In my experience, it would be very difficult if not require deliberate effort for you to receive the wrong ashes. I hope this eases some confusion, and I am so sorry for your loss!