One of my elder sims died while I was playing another household and now I can't find his urn&tombstone, so I don't have his ghost to work with. (in terms of workarounds & cheats)
I mean if I see his ghost I could just add him to the active family via testingcheats+shift click, then buy an urn via showhiddenobjects cheat, have the ghost posses the urn and viola. But I can't reach the ghost.

My alive sims still have his picture in their relationships tab. I just want to place his grave next to his wife's. If I had his ghost I know what to do but I don't know how I can spawn the ghost when there's no urn&tombstone. Any ideas?

Edit:
THE SOLUTION

I wanted to share the solution in case other players have the same problem at some point so they can see this when they google it. Ok, this isn't a very quick and easy solution but it's the only one for now. You have to bring the ghost to life and kill it again in order to get a proper urn. (debug urn won't work)
1- You need MC Command Center mod in order to summon the ghost of your dead sim. After you download and install this mod use your mail box to summon the ghost.
2-Once the ghost is at your lot, turn testingcheats on and shitf+click = add to family. Now that ghost is playable as a part of your family.
3-Now you need to cook ambrosia and have your ghost eat it. (check ambrosia guide) For ambrosia ingredients, you can get the death flower and the potion of youth from debug catalog, but for the angelfish, you have to get it via fishing.
4-After your ghost becomes an alive sim, you can now kill them either using MC command center or however you want.

If they have his picture - have you tried having one of them call him and invite him to current lot?

That was the first thing I tried . When I click on his pic, no options pop, nothing happens.

Can you summon him via MC Command Center?

If you have Get Together, see if he shows up at the bar for Ghost Night.

I don't have the mc commamd center (i guess it's a mod?) But i can try that. Also the ghost night seems like a good idea worth a shot but how do I trigger it? May be by adding a random ghost to the family... hmm
Thanks guys i will look in to those.

edit: ok ghost night is 8pm to 2am on wednesdays. lol I didn't even know there were different special bar nights everyday. never payed attention to that before. let's check there first.

Ok, I had no luck with the "ghosts night" but MC command center worked like a charm. I summoned the ghost. Thanks @audioromance

I thought I saw in the load screens that a ghost could use the Wishing Well to come back to life for one simoleon. If that is true, it may save time trying to get the ingredients for the ambrosia. Just a thought.

Do we even have a wishing well? (other than the decorative one that comes with get together?)I had no idea. I will look in to that lol

The wishing well comes with romantic garden stuff so if you don't have that then you don't have it. I'm glad I could help. Seems a shame though you can't just ask the ghost to spawn their tombstone you'd think they would know where they died lol.