Correct, for the most part. The enemy is not targeting the square, he's targeting you.
However:
If you were invisible before you teleported, then the enemy -would- be targeting the square and it would be a miss.
If that enemy had charged you, he would have had to make his attack from three squares away, as that would be 'the closest square from which he could attack you' and the teleport should have worked in that situation. Also, you'd have known he had reach 3.
The interesting thing is, reach isn't a surprise. Generally, if a monster has reach 3, it's pretty obvious, and the party should have been made aware of it at the beginning of the encounter. No, son, you cannot hide the ability to smack someone 15 feet away in your back pocket.