Invisible Ivern brush

So I played a game tonight against an Ivern in top lane. He made a patch of bushes on the wall basically where the river meets toplane. The brush looked weird and seemed to be half in the wall. Ivern walks into them, while I'm under tower. I moved towards the brush to try and force him out, and it disappears. I assumed that it had simply expired and Ivern had walked out the back without me noticing. But as I move up in my lane, Ivern just appears from the wall where the brush had been. Not sure if Ivern went invisible, or the brush with Ivern inside it did, but either way, it made for a bad time.