Here's an excert from Pat Forde's column on Yahoo Sports that helps clear up some of this.
The hoax started coming to light in early December, according to sources. While attending the ESPN college football awards show in Orlando, Notre Dame athletic director Jack Swarbrick said Te'o got a call from the phone number he had associated with Kekua. Te'o was deeply disturbed by the call and suspected it was Kekua's purported sister. Although Te'o's parents were with him in Orlando, he did not inform them of the call, a source said.
The person kept calling and saying it was Lennay herself, and over the course of 10 days Te'o engaged the woman in several conversations.
"He was asking questions only Lennay would know," said the source, adding that phone records show multiple calls between Te'o and that number.