hi tjones
when you place images in scribus, they are normally linked to the .sla file, not embedded. (well, it is possible to embed them, but i wouldn't recommend it in most projects…)
when you move the images or the scribus file on your drive, the .sla file will lose the link and the red cross with the file name will be displayed.
if you have to move your scrbus project, you should use 'file' → 'collect for output' to generate a project folder with all the images (and the fonts and color profiles, if you need them).
utnik