LOL! I’m glad I’m not the only one who did this. I bought a similar small animal heating pad for my buns, because I have their cage downstairs, which is significantly cooler than the second floor, and we have fairly cold winters. During the first cold snap a couple of weeks ago, I dutifully plugged it in and waited for the bunnies to try it out. They did hop on the pad a few times, but other than that pretty much ignored it (in fact, I think they were giving me dirty looks for taking up half of their party deck with a hot mat they found uncomfortable).
The next time I went to see the vet, I asked how cold was too cold for my rabbits, and she almost laughed. Basically, unless it’s so cold I can see my breath, she doesn’t think the rabbits will be bothered. Unless I lose heat altogether, and am not home to move them upstairs, they probably won’t be interested in the pad at all. At least it didn’t cost a lot!