Can't Find Deceased Pet's Urn

@Carlz916 For a pet you don't feed them regular ambrosia... The Sim can serve a deceased pet an ambrosia (pet) treat to 'resurrect' them. Go to the vet's vending machine and purchase an ambrosia treat (made for pets). With this treat in the Sim's personal inventory have them go to interactions with the pet's ghost and under 'friendly interactions' you should find 'give ambrosia treat'. 

Hope this helps! 🙌

How do I get dog to eat ambrosia? 

This exact thing happened to me, and it was so annoying! I search high and low all over the web and forums for an answer, and finally i found a solution. Here is what I did.

1. Turn on cheats and find the dead dogs ID numbers using this cheat: sims.get_sim_id_by_name [PlayedPetFirstName] [PlayedPetLastName]. Get each one individually and make sure you copy the number down so you don't forget it.
2. summon the dog to your house by using this cheat: sims.summon_sim_to_zone simID 
3. once both the ghosts of the dogs are at the lot, add them to your family (shift click on them, press add to family)
4. Then you can take them to the vets, buy ambrosia treats for both of them and bring them back to life
5. they will come back to life as elders, so will live in that stage for a bit, and eventually die of old age, leaving you with the urn/gravestone.

If you want them to die immediately then you can find cheats to kill them: traits.equip_trait Ghost_OldAge [Pet ID]

I hope this helped you! It really helped me.

Unfortunately locks do not work when you are not playing that household. As far as I know there is no way to know for sure that they died off lot. Try to go to manage world | manage household and see if the ghost are there.

Well that's lame. They shouldn't have been able to leave the house because all of the exterior doors are locked for pets. How can I tell if they died away from the home lot?

Yes, I checked the household inventory and each individual Sim's inventory, but it's not there either.

Did you check in the sim's inventory for the urn?

If the pet died away from home lot there will not be an urn.