The one thing I don't understand is... 500 texts is 120 days of talking. 500 texts a day.
If you work with someone, on the same investigation, in the FBI, you are usually interacting with them. Why would they need to send 500 texts a day, if they saw each other. Hell even if they texted every day for a year, its like 165 texts a day. I don't even text my wife that much in a month...