The cub always appears at the Goblin camp if I do the following:
- Leave druid's grove. Bump into the siblings and dead Edwin. The siblings have a quest at the owlbear cave. Convince them to go somewhere safe (so they don't aggro owlbear if you don't plan on attacking).
- Go to the owlbear cave. Used speak to animals, talk Owlbear mother down from attacking. Leave the cave immediately. If you do plan on attacking the owlbear mother/consort, leave the cub alive.
- Longrest, then go to the goblin camp
The owlbear cub did NOT appear at the Goblin camp if:
1. I went to the Goblin camp before talking to the owlbear mother. If you go to the Goblin camp first, you get a chicken.
2. I talked to the owlbear on the same day and did not longrest for the goblin raid to occur.