Don't place it on top of any heat source. Pacs burrow to stay cool in the wild, and if the heat source is below them, they don't realize that burrowing won't cool them off. They can overheat/dehydrate and die if this goes on for very long. I would recommend sitting him near the radiator and maybe wrapping the heat blanket around two sides of the enclosure. Even when you get a heat pad from the pet shop, be sure to put it on the side and not the bottom.

If you can go by a walmart or hardware store before then, you can pick up a 40 watt red bulb and one of those outdoor light fixtures with a clamp on it and sit that on top of his tank for a heat source. Since you don't need UVB, the red bulbs in hardware stores aren't really very different than the expensive ones they sell for reptiles. :P Just be careful and make sure it's not a fire risk when you set it up.

Here is the link to the Trouble in the Enclosure thread
http://www.frogforum.net/pacman-frog...enclosure.html

This is mainly just to make sure everything else is good (because even the smallest problems can cause pacs to stress out and stop eating).