My 2 cents on the subject: As long as you're allowing the toad to regulate her own body temperature by having a thermal gradient (warm and cool end of the cage) it can't be doing too much harm, since she can move if she is feeling too warm. I've never had to heat my toad, since my apartment is usually in the mid-70s regardless of the season.
You might want to get a temp gun like this:
Amazon.com: Zoo Med ReptiTemp Digital Infrared Thermometer: Pet Supplies
This allows you to measure the surface temperature of the substrate and not just the air. You can actually hold the button down and move it around and you'll see the temperature change in real time. Very useful for anyone trying to provide a specific belly heat to his/her critters. (I have leopard geckos too and wanted to make sure their warm side of the habitat was exactly 90 degrees.)
I'm sure most would agree that it doesn't really matter where your pets come from in terms of what you'll do for their benefit. You will feel the same happiness and loss from them whether you got them for free or paid a pretty penny. I found my toad hiking when she was just leaving the water as a 1/2 inch long toadlet. There were actually hundreds of them, and unfortunately they were coming out right next to a heavily-traveled trail head and many were being stepped on by hikers who didn't notice them. I scooped up three of them, and only one ended up surviving to adulthood, even in much safer conditions. My hamsters were free too, because they were injured and needed a home. Still love the little fuzzballs (when they slow down enough for me to see them, which is rare.)