Disappearing Headstones

I created a graveyard who knows how long ago in my game, long before they gave us the Life & Death DLC. I have been playing a legacy game and I have several generations in this graveyard. Once we got the Life & Death expansion pack, I was able to change the lot type to Cemetery, and then I wound up moving the darn thing. Anyway, long story short, When I placed the lot from my gallery, ALL OF THE HEADSTONES DISAPPEARED. All I had when I put the lot down was the flowers I usually place at the grave sites (and the vase colors had turned from what I originally had them to the standard vase). I solved this problem (very tediously, mind you) by putting the tombstones, AND the flowers into a Sims' inventory, and placing them all down the way I had it. Anyway, ever since then, random headstones that were there before are gone. I can NOT get them back, because the ghost of this character has faded away a long time ago. This has NEVER happened before, and I also don't understand why the headstones DON'T carry over when you save the lot to begin with (I have 124 headstones in that cemetery, and believe me, I do NOT want to lose them all!) So what is up with this, and is there a solution to this problem?