Turret Not Agro'ing Champions [GAMEPLAY]

In my last game I played I was top lane as Lee Sin playing against an enemy Zed. Early on Zed dived my turret two times in the first 10 minutes of the game without taking ANY turret agro whatsoever. Both times he had minions pushing into my turret however he always auto attacked me while standing within turret range so I'm one hundred percent sure he should have obtained agro from the turret. The first time he threw his shadow under my turret and went on his shadow, auto attacked me three times then simply walked away. The turret never changed agro from the minions. The second time he used his ult onto me, auto attacked me a lot, at least 3 or 4 times if not more, then used his shadow to escape once again pulling 0 turret shots. I've never seen this happen before and I was shocked because I was sure in the first scenario that he should have died. The second one I can't really make proper judgement on but I know the turret should have hit him at least once or twice. I did not record this particular game so I cannot provide the replay, however I really would like to know if there is some way that this can be checked into to ensure that I am not going crazy.