Thanks for the response. I had cleaned the enclosure with a reptile safe solution and had been using ReptiSafe in the water so I can't see how it got exposed to any chemicals. There were no decorative items disturbed and apart from plants there were no items far enough of the ground or light enough to be tipped. The top of the enclosure was clipped shut in several location so I don't think it could have budged it. The thermostat and ambient temperature were still good when I got back, so I am not sure if it temporarily malfunctioned or not.