Memory card pictures lost

Hello,
This is the second time this has happened in the last month. I don't know if its my memory card or my HP printer that's making my pictures disappear. I've taken nice pictures of my kids and I can look at them in my camera delete the ones I don't want, shut my camera off and back on and my pictures are still there. I did this numerous times to make sure my pictures were on my camera and in the memory card. Took the memory card out of the camera stuck it in the HP printer like I do every time, clicked on the card on my desktop and my pictures are gone. Put the memory care back in the camera and they are gone off there too. Can't find them anywhere. PS. I use a Mac lap top. Not sure if that matters for trying to get pictures back. I've take picture in between the two sessions of losing these pictures. I just don't get it. When I take the nicest ones I want to keep then they disappear twice.. Can anyone help or are my pictures gone for good.