A ridiculously sealed note is left at Castiel's place. When he finally is able to open it - why? so much tape?? - he'll see the following message written in a surprisingly neat cursive script:

Hi Mr. Castiel,

I wanted to let you and the others who fell asleep during the events and had dreamt of the past(?) of Beacon this info: You can write to Dr. Solis and share your experience with her. I don't like doing this but I really hope you do. Mr. Ignis was unable to experience the full thing himself and that means some details are still unknown.

You can leave your letter over at the Post Office whenever you want to get around to that. Postmaster General will send your letter to her.

Thanks,
Daylight.