I haven't been able to find this one and it's driving me crazy! It shows between Naru and the Xenosheet in the Funhouse Ghostiary and the silhoutte kinda looks like Japes. I assumed it had something to do with blackouts or drilling through walls but I've had no luck. Can someone help me out with this one? 

you're not alone, pango.

For anyone in my same situation looking to get around this, you can alter the spawn rate in the json file. I got so desperate that I read the modding guide for the sole reason to change the spawn rate to finally be able to see this ghost.