Minion Aggro Bug

I encountered this recently in a match with Vlad and Teemo. Maybe I'm missing something, but I could not find a single reason why the Temmo didn't draw any minion aggro in the video linked to this post. Any ideas? Or was it just broken? I tried a custom match after this to see if I could reproduce it, but I was drawing aggro in testing.

Edit: Uploaded to YouTube for convenience: https://youtu.be/k_JTBjqA-g8