Tiamats passive did not pop.

I just played an ARAM as Shaco. I went AD but had AP runes/masteries because I wasn't paying attention. I had a Lord Dominkis regards, Tiamat, Long sword and boots. The passive for Tiamat would not proc, neither the damage or the animation. I died and respawned a few times and it still occurred. The active was still functional however. Once I completed the upgrade to Ravenous Hydra, it worked fine. The animation, damage and active all seemed to work without issue.