In such cases, you have to follow some techniques to retrieve the information of the paper. Some techniques are described here. Here you should remember that all kinds of thermal papers do not come with same quality and materials, the techniques may not work with all kinds of papers satisfactorily. You should not do the processes without caution; if you do not follow the processes cautiously you may have to lose the faded information of the thermal paper.
As the first technique you can follow the camera technique. Take the digital image of the fadedthermal paper; then enter the image into the computer. Start a photo editing software and start to retrieve the information. Apply all the techniques that you know to clear an image. You can also try the invert filter options of the software to retrieve the information. As the second technique you can try to retrieve the information with the help of a photocopier. But be careful, after entering into the photocopier and getting light from it the paper may become totally dark, and you may lose the information that is written on the paper.
As for caution, cut a small piece from an edge of the paper and copy it using the photocopier. If everything is ok, then you can copy the thermal paper by adjusting the settings of the copier to make it readable in the copy. If this recovering technique does not work, then you can check the laminator technique.
Before proceeding with this laminator technique, test a piece of the thermal paper as you did before in the photocopier technique. If the piece of the thermal paper becomes readable after running it through the laminator, then you can proceed with this technique. The heat generated from the laminator may make the paper readable. If you do not get the information in this way, then you can take the help of a scanner to retrieve the data on the paper.
The heat and light of the scanner may help the chemicals to activate and make the paper readable again. To protect the non-text areas of the thermal paper from the scattered light you can cover the thermal paper with a piece of black construction paper. To be sure enough you can check the process with a piece of the thermal paper as you did in the previous techniques. You can also use the iron or the hair drier to heat the faded thermal paper to activate the chemicals of the paper again. Any of the above techniques you can follow, but you should do it cautiously.