Image pasted into document isn't saved

I copied a screen grab, pasted it into a document, made sure to do a File|Save, then exited. On re-entry, all the rest of the added text appeared, but the image was lost.

Not seeing that behavior here. Grabbed a screen image, Ctrl-V to paste into a document, resized it, added text, Ctrl-S to save. I then moved around the binder for other documents and folders, when I came back the image was still there. Closed the project and reopened, the image was still in place. Completely closed Scrivener, then opened it up again - the image was still there. Not sure what to do to duplicate your issue. Sorry.