(1) Those things decay with time. If you've got one for something valuable, scan or copy it for your records.
(2) I suspect if you took a black and white printout of a picture (maybe in reversed colors) and laid it on some of that paper and exposed it to the sun, you'd get a print of the picture on the receipt paper.
Along about 1946 my Pop showed me how to do "thermography" by laying a negative on some regular photgraphic printout paper and exposing it to the sun for X minutes, and a brownish image would appear. It didn't last long (days), but some brownish silver complex formed where the light went through, yielding a positive image.
You might try it with this on some receipt paper or even old-fashioned photo paper if you can find any:
(Hope that's OK with you, KD5NRH. If not, I'll change it.)
I've got some more oldey-timey oldey-pharty photo tricks I'll 'splain later.
Terry, 230RN