I think that the helper was Morindin. The reason that Rand does not feel the channeling is because the True Power is being used. Remember, Rand can 'feel' saidar being channeled with the goosebumps he gets. Besides, Osan'gar is a female using saidin, not a male using saidar. We also know that Morindin has used the True Power because of the saa showing in his eyes when Moghedian talked to him.