One thing I've noticed about OWoD, is there is a lot of ST discretion involved, at least from my experience with it. Blur of the Milky Eye does indeed say it affects Perception rolls, but the description of the Gift I feel matters just as much as the mechanic. The description says nothing about Sight or Sound in terms of what it's hiding, and when I run games, I would make it very clear that this Gift isn't going to hide them if someone can track easily via scent. A Vampire with high levels of Auspex, or a Garou with Heightened Senses on could potentially track via smell, or even heartbeat...