SA says he didn't delete any calls in his interview. Billie says he admitted they were there, police gave him his phone back, and then they were gone. Poof. "Vanished into thin air"... I think maybe they were questioning him, they looked at the calls, left the interrogation room and watched him delete those calls. So, they got to take the phones (which is good, didn't need to wait for the call logs, just check the deleted call register on the phone).
GRACE: When we were told that -- when police wanted to look at his cell phone, he started deleting numbers, did he explain that to you?
DUNN: What he told me was, they wanted to see where he had called me at work. He showed it to them on his phone. They said, OK, gave it back to him, and they said show me again. And he says it wasn`t there.
http://transcripts.cnn.com/TRANSCRIPTS/1101/13/ng.01.html