It knows you surf
Ah, of course - who in their right mind would want Rule 34 of Bryan Cranston and god forbid...Robin Wright, right?!
If it is in your home, one would assume a great many things would smell like you, namely your clothes bed, couch, fridge, chairs, table, door handles, bathrooms, and any number of other things that would all register as false positives were that the case.
I agree with you on that, but it makes a lot of sense as the culprit would probably have used the drive quite a lot, especially during certain acts *no further descriptions needed*, I'd expect certain secretions to become transferred to the surface of that drive making it unusually easy for any dog to sniff out. You know how small micro-SD cards are, right? Imagine someone hiding it in-between the wafering of a cardboard box, or perhaps a crack in the wallpaper? Surely that must give off the odor of the contaminated SD-card rather than the wallpaper? It's not like you touch the wallpaper all the time etc.?
Still plausible in my world.
There's got to be more to life than compile-and-go.