User blog comment:ImperiexSeed/Supernatural Mysteries/@comment-3481504-20120501201343/@comment-3045936-20120502155523

Well. Samuel didn't know much about Angels after he was brought back in season 6. Sam told him some general stuff and Crowley too. Also, when he saw Castiel he said your castiel? as Souless Sam might have told him some general information about Angel lore. But Soulless Sam said in you cannot handle the truth that they needed in that nest, and that Dean could handle it. So it makes sense that he wouldn't have calls Cas at least until after the job was complete.