Jackie, that used to happen to me. I would post scans of my paintings and then suddenly find out that a post I made in a different forum had the new scan rather than the painting I posted there. I did something like a flower in oil pastels and the description in the thread said it was a cat sketch, or the reverse. It got very frustrating. Anything I posted would go replacing previous paintings in other posts.
A moderator sorted it out for me by asking if the scans had unique file names. They didn't. My scanner always gives names like IMG, IMG0001, IMG0002 and so on to them and I hadn't renamed them before posting. So of course the IMG0001 that was a cat got overwritten by the IMG0001 that was an oil pastels flower. I had to go back and fix some old threads, uploading renamed versions of the right files for them.
Then I got in the habit of opening all my scans and titling my files with the title or subject of the painting, sometimes adding the medium or date with it if I was pretty sure I'd drawn that before. Otherwise I'd be deleting a lot of "AriSleeping.jpg" files, some of them photo references and others sketches. Or confuse people by their seeing my latest photo when I said it was a colored pencils drawing! (Great realism, looks just like a photo!)
So check your file names. If you have duplicate file names WC will replace all earlier versions of anything that shares that file name. (Flowers in the Animals and Wildlife forum, oil pastels in the Drawing and Sketching forum, all sorts of mixups before I found out why it was doing that!)