Sniffer dog detection is another of those somewhat dubious things, since detection is only partly the dog's olfactory ability, but more the handler's interpretation, plus the dogs react to cues – subconscious or otherwise – from their handler. So if they think you look sketchy as you malinger by your badly hidden p0rn stash, the dog may be pleased to oblige its alpha human buddy's gaze at that box by duly sniffing it out. I'm unconvinced that a sniffer dog can genuinely find an SD-card, sounds more like a bit of a wriggle to fit within terms of the search warrant.
Most people don't understand encryption. I wonder what happens too, if it's all encrypted, Apple for instance have Filevault on by default. I might be wrong, but the latest iteration must be pretty tough to crack if you don't pony up the key. Not sure if Microsoft do something similar, but setting up encrypted partitions and storage isn't super-complicated. But given the (non-child) p0rn I've seen smeared across nearly all the computers I've been asked fix over the years, curating that collection hasn't been high on the owners' agenda.
Edit: sniffer bees are a thing, though. Sort of.