Warding hopping to a swept ward

I playing a game a few weeks back and had a Jax hop on a swept ward. I was in the bush at the very bottom of the river, slightly across from the dragon pit. I saw Jax place a ward so I quickly swept it to avoid him being able to jump the wall. In the midst of killing it, all of the sudden Jax jumped right to it. There was two things about this that didn't make sense. One, the ward shouldn't have been visible to the enemy. Two, the ward should be disable from any actions to it. I haven't looked into it sense then so it would be interesting if anyone else has the same thing occur with lee, jax, or kat.