Unfortunately there are lots of weeds that grow naturally in your own yards that could cause listlessness, hallucinations, and general stomach upset. There also could be some flowers, mushrooms, etc... that go undetected by you, but look like a treat to pups. You also have to consider pesticides being blown into your yard from a neighbors' house, or contaminated water from the rain. With so many factors to consider, you may never be 100% sure of the culprit, but you should definitely take her to the vet if it lasts longer then 1 day. Good luck~~~~