email moved from Junk folder to inbox seems to automatically revert back to Junk folder

This keeps happening, and I usually catch it and move them again to my inbox. However, today I moved about 6 messages - they no longer appeared in the junk folder, so I then emptied the junk folder. About an hour later, I checked my inbox and the messages aren't there. They are also not in any of my other folders, nor are they in the Deleted folder or the Junk folder. I need to reference one of these emails and it seems to be gone. How can I get it back? Thanks.