Well, although i had a different opinion at first, they really could have been looking for data carriers and similar stuff.
www.ndr.de
"Gradually, the tasks became more difficult - mobile phones, SIM cards, USB sticks. Joker finds almost all of them now, even if not right away. After Joker had internalized the smell of an external memory card, he should find a model from another supplier. At first without success. Häusler thought they would now have to teach him every model from every manufacturer. "That's too many, that would be impossible," she says. But Joker quickly understood that he had to show his display behavior even with similar smells - and was rewarded for it. He saves newly learned scents immediately and can call up the knowledge later."