In dev mode, we can see “Created {time} ago”, and a button to see what changed, who changed it.
But we can only know who created it if it is modified at least once.
In other words, if it is created & finished within a same day, we cannot know who created it. Especially in a file where multiple editors collaborate together.
I think Figma should have a text somewhere telling “Created by” near that timestamp in Dev Mode or somewhere in viewer’s Properties panel.