I am sorry you are having this problem. When was the last time you saw them there? Have you recently cleared your cache or re-installed the browser?
Unfortunately, if you are using the same browser on the same computer and they are no longer there, they are most likely gone forever. his could happen if, for example, you cleared your cache in the browser, used a utility which cleans your computer, or ran low on disk space (additional possibilities are listed in the first document referenced below).
I said "most" likely, because there are steps you can take to rewind your cache if you had already been backing it up, but most people do not do that. My primary platform is Mac and I back my browser cache up with Time Machine on the Mac, so I can go backwards in time and restore my cache from a point in time. This has saved me a few times when something was deleted from my cache and I was able to roll the cache and settings back a day. If Windows was my primary platform, I could do something similar on it.
For a complete description of existing features to save prompts and images, please see these documents: