Today in my site statistics it shows the average number of visitors but twice as many page hits. Of course, this could be a simple, random inconsistancy. However, if this continues I may begin to attribute it to hotlinking/stolen bandwidth. I haven't made any significant bandwidth-raising change to the site in the last day.
Is there a way to check if another site is calling in my files?
As far as checking if someone is hotlinking, viewing your raw access logs for HTTP_REFERER would be a good idea. Finally, you should protect your image folders from hotlinking with mod_rewrite anyways.
If you have AWStats, then look at entry page. If lots of them are an image or a download, then people are hotlinking to your files. If it is an actual page, well, that is all gravy. You do want visitors after all.