Old tips are old.     Like base game only old, so I don't know if they'd work with EPs...much less animals.

- Along the lines of what Prof said, have the ghost-questing sim stand in the spot your ghost last stopped drifting and disappeared.  The ghost might return to the same spot and scare your sim for the memory want fulfillment.
- Buy a teddy bear.  There's an option to 'Talk through to...' or something to that effect, and if ghosts were out, their names would show up in the pie menu list of those to bug with the bear.

I recall having a success or two with the first suggestion, but not so much the second.