What do they think it was?
I can understand them backing off the mid-air collision idea. An Embraer Legacy 600 is a large business jet that's based off the ERJ-135 commuter airliner; the ERJ-135 seats 37 people normally (the Legacy has a plush interior for about 12-14). A loaded 737-800 has around three times the mass of that Legacy and is at least twice as big in all dimensions. If a 737-800 struck a Legacy, unless the Legacy was incredibly lucky and the 737-800 incredibly unlucky, there wouldn't be a crew left on the Legacy to detain somewhere. Both planes would have gone down.
Both planes are also pretty much state-of-the-art, with glass cockpits and full TCAS (collision avoidance systems).
It's possible there was a mid-air, though, certainly. It would be a big coincidence to have that 737 disappear and have another airplane make an emergency landing nearby in the same general timeframe.
}:-)4