Thermostat issue-shop

[cmyoung2]

Installed a propane Mr Heater unit in the shop this winter, worked fine, no problems. This weekend it got a little warm here, maybe upper 70's. Shop is a metal quonset hut type building, so with it shut up I'm sure it got a little warm inside. I got home about 6, heard something running in the shop, stepped in, and the heater was on, so it was really hot inside. Turned out the thermostat had shorted, turning the unit on. And yes, the T-stat was at the off position. Turned off at the breaker now, will get a new t-stat before winter. Something to think about.