I have no problem with there being an investigation. I would welcome it. I think you need to do a little more reading if you think intelligence is gathered by just "checking back" on people. This isn't an episode of 24.
Federal agencies do not have the resources to just wiretap every person they have any intelligence on. They have to sift through mountains of intelligence, both foreign and domestic. I would imagine the amount of information they get from both sources is so vast that prioritization would likely put intelligence from a nation we have strained relations with (assuming it is Russia) giving us info on an ethnic Chechen, a people Russia has strained relations with, and a people which also does not have a history of poor relations with the United States, at the bottom of the list. That's just my take on the subject.
These rope devote their lives to their work, but they're also human. They do make mistakes, and I would welcome a decision for an investigation. A mistake is one thing, but any sort of cover up would be serious business.