Question: Why didn’t Comey and his 150 clowns find these 15,000 emails?
Answer: They lacked the necessary resources.
All the FBI needed to do was ask the State Dept to search its e-mail archives for Hillary’s e-mail ID and sort the results by recipient. There would be some cleanup needed, but large organizations search for e-mails all the time for lawsuits, personnel issues and the like.
The entire issue is that she wasn’t using the State Department’s email system. Sure, they could have found some of her emails by doing that, but only if another State Dept employee was cc’d on the message.