If your pictures aren't there anymore, consider them as being deleted, but they actually aren't completely. Consider installing the software "Recuva" on your computer and running a "deep scan" on the root of the memory card (for example it could be the letter "F:", but not a subdirectory like "F:\DCIM\"). It might take a while as it has to scan every single cell on the card. If it finds anything, you can restore the files marked as green (files which are still intact and not overwritten; those will be orange or red).
If the software doesn't find anything, you might need to display hidden files, and system files as they could be in a "recycle bin" (or any possible system folder) inside the memory card, and not considered yet as removed because they are still taking the memory card's space.
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