Lau’s self-indulgent headcanons: Castiel heard Sam’s invocation and lent a hand in saving Bela’s life.
[Caption: gifs from s03e06 of Supernatural. Sam and Dean perform a ritual to spare Bela from a ghost that’s haunting her; Sam performs the invocation while Dean stays next to Bela in the rain. The ghost almost gets to her, making her vomit water as if she were drowning on land, but Sam completes the ritual, summoning the ghost’s brother and having them disolve in water together, while Dean holds Bela and checks if she’s alright. Coincidentally, one of the names summoned at the beginning of the ritual is “Castiel”.]