Glommer despawns when you leave him in another room in the shanty, even though his flower is still there.
Steps to Reproduce
Hop over to RoG with a key to the city. Build a slanty shanty. Put Glommer inside the shanty and then walk into another room or step outside. Go back into the room. Glommer is missing.
Hop over to RoG with a key to the city. Build a slanty shanty. Put Glommer inside the shanty and then walk into another room or step outside. Go back into the room. Glommer is missing.