UGH, I KNOW!!!!! i even freaking emailed ZooMed to ask why they don't just manufacture a thermostat right in, and they gave some TOTAL BS response that indicates they actually know nothing about their products. i'm not sure if i still have the email exchange, but i will see if i can find it to post for you guys.
OP, good job on unplugging that heat mat, they can be very dangerous if you don't fully know how to use them. luckily you found this great site!