Dump 100mg of cadaverine in the thiefs car and they'll never use that car again. And possibly the clothes they wore at the time.
Or other chemicals.
It would be most exciting to find chemicals that yield strongest short-term effects without any damaging long term effects.
As far as I'm aware, it's the worst smelling chemical known to humans and has no damaging long term effects. You just have to be veeery careful about it unless you want to stink up the whole town by accident.
Kidding of course, but I it makes wonder how easy this would be for an amateur to synthesize. The consequences being making an entire town nauseous makes this whole thing pretty enigmatic.
The packages were some rolls of vinyl, a box of sealed granola snacks, and some inexpensive jewelry, all rejected by the thief. If the person was homeless, I'm surprised they ditched the food, it was nutritious and shelf-stable. (I redelivered the packages.)