I've had this problem more than once, and with a bit of luck and some intuition found a method to restore the thermal "image".
By gently heating the receipt at a distance with a hair dryer, I have been able to cause the original images to reappear. Note that too much heat will cause the entire receipt to darken, so you may want to test temperatures/distances on a blank area, such as the corner of the receipt.
Generally, a hair dryer on medium heat at a distance of 12" or so, waved slowly back and forth, can restore the original thermal image in under a minute. Your mileage may vary.
Slashdot Mirror
I've had this problem more than once, and with a bit of luck and some intuition found a method to restore the thermal "image".
By gently heating the receipt at a distance with a hair dryer, I have been able to cause the original images to reappear. Note that too much heat will cause the entire receipt to darken, so you may want to test temperatures/distances on a blank area, such as the corner of the receipt.
Generally, a hair dryer on medium heat at a distance of 12" or so, waved slowly back and forth, can restore the original thermal image in under a minute. Your mileage may vary.