Two other details that makes us perform comparatively worse than dogs, at this sort of task:

• A lot of scentful substances are rather heavy molecules, so they tend to go near the ground, closer to the dog's nose but further from ours.
• Humans have damn good vision. We simply gather more info from visual than olfactory clues, so we tend to undertrain the later.

I have a friend named Dave who wore so much patchouli that, if I went by his house within twenty minutes after he left, I could follow his trail through the open neighborhood and find him on scent alone.