I just noticed something odd. The family cat just died and I was moving it's tombstone into the family cemetary I made behind the house. I had put the tombstones for three sims there earlier (at different stages). All of those tombstones are now gone. Is there a bug in Sims 2 that puts a time limit on the amount of time that tombstones can be displayed in game or could this be something else?

This seems to crop up every once in a while. Have you patched all of your games?
I've had tombstones disappear from cemetaries, but not from a residential lot.
Pescado's lot debugger has an option to respawn the tombstone:
http://www.moreawesomethanyou.com/s...topic,72.0.html Snag the version for your game config in the Armory>Hacks, All Hacks. Make sure to read the manual on how to respawn the tombstone (which requires debug mode aka:boolprop).

Appreciate the help, but I can't figure that object out. Also I tried the ressurect-o-tron and none of the dead sims show up in the list (although that could be because their data is kept in the tombstone which is now gone...) I guess I'll have to do without them although it buggs the bejesus out of me.

I believe you need to use the recover tombstone option in debug mode (AKA Testingcheatsenabled true). If the charector data isn't shredded, the option *should* appear. You can always post nicely in the thread for detailed instructions. Watch your punctuation there, and be polite (just a heads up).