The mystery would not have confounded Sherlock Holmes. It probably wouldn't have confounded a six-year-old, blindfolded child.
The crime scene:
Clues of note: the plant was a catnip plant, recently removed from its enclosed plastic greenhouse and transplanted into an open can. This can was placed on the ground at approximately cat-eye-level.
Relatedly, a cat (a.k.a. "Acouchi") was also recently transplanted, from the vet clinic where she had spent the last week and a half getting radioactive iodine treatment for hyperthyroidism, to the home where the crime occurred. The alleged cat was suspected to be harboring intense feelings of hatred towards those responsible for putting her into the vet clinic for a week and half, as well as a love of catnip. She also had no alibi for the night in question.
Perpetrator: "Who's hiding it? And tomorrow night I'm peeing on your beanbag chair with radioactive pee."