Can't place my gravestone from household inventory

@crinrict I tested this out on a new save and it worked fine. It might be because in my existing save I rotated households while playing and when the sim died I was with another household and didn't get to witness the death but I'm not sure. Also the gravestone was actually an urn but I don't know if that has anything to do with it. I'm trying to think of what else it might be.