Indeed. A real investigator would request the Call Detail Records from the NSA. They get copies of everything, even if they aren't actively recording specific calls.
A real investigator would have wired up the “flipper” and sent him in to corroborate the allegations. Sending in someone after letting out the rumor can backfire simply because when someone shows up or calls out of the esters to comment upon something that happened years ago, the target usually becomes uneasy and utters the following: don’t recall what you are talking about. The is extremely exculpatory evidence.