I reckon I'm pretty good at recovering hidden files. (For example, I bought a laptop at auction that had a BIOS password on it but found a way around that. Having removed the BIOS password, I then found that there was also a Windows password on it but I managed to defeat that too).
However I've never heard of any way of recovering image files from a printer/scanner. To the very best of my knowledge, it would be totally impossible because any file handling is either done by the associated computer anyway or using files that are only stored in short-term memory. (i.e. the data is lost as soon as the printer is turned off).
Further, I've never heard of the police (investigating, say, indecent photos of children or the production of fraudulent documents) ever seizing a printer from a suspect's home in the hope of recovering data from it. They, like me, clearly seem to think that it's simply not possible.
Relax ;-)