I'm not sure if you are meaning to ask about links inside
topics that point to images that you are popping up or linking to
outright or if instead, you mean that some of the images that are
supposed to be displayed inside topics are maybe missing and you
wish to know about them.
One easy way to spot a missing image reference is by using
the Project Manager. Not sure if you are using RoboHelp 7, 8 or
older here, but if on 7 or 8 look in the Project Manager pod.
Otherwise it will be found on the left panel of the application.
Expand the Images pseudo folder and quickly scan the list of images
and expand sub folders inside. Any missing image should be listed
with a red x to indicate the status. You may then examine the image
properties to see which topic(s) is/are still referencing it.