Monitoring foreign chatter and picking up indications that countries got information that they were very much not supposed to, and then finding out that said information was part of what Trump brought with him down to FL. Picking up on external communications similar to the Trump Tower stuff from the campaign days and investigating further. There are plenty of options.
That's...absolutely ludicrous and bordering on the line of a conspiracy theory, dude.
Again, unlikely, though it's doing wonders being in-line with the "THIS WAS A DEEP STATE SETUP!" type arguments we're seeing all over the place.