Image 'noise' or gray on saved Indesign files

I've started 'losing' my images on saved files.  It's fine as a work on a document over a period of days but it seems to happen after I've archived it to an external hard drive.  If I need to call that file up again, even after a period of a few weeks I get this 'noise' in the image frame and the tiny pic in the top corner. Or the frame is greyed out completely. I've posted a screen shot as it's probably the best way to show what's happening. The link is telling me that the image is still connected. I've looked at the display preferences on my Mac and the display performance is set to high quality. I'm not that technical but I don't know why it's suddenly started or how to fix it.