Outside of sending everybodies shoes who walks through an airport to a forensics lab, how do you even find that minuscule of an amount?
Usually technological gadgets aren't as sensitive as the dogs are. However, if I remember back from my college days what a gram of pot looks like, I would think that 0.01 gram would be noticeable, and even in tiny quantities the stuff stinks until it dries out.
You wouldn't be able to just smell it on someone, but if you searched them carefully and found a tiny little bud, you might know what it was from the smell. Then they could test it to make sure.