You're most certainly not an idiot for missing or forgotten image metadata. And Cocoa is a cute one. I am glad to meet him, even sideways.
Cute kitty. But why kitty disoriented? Here I reorient the kitty:
Now kitty is happy! 😺
On the web interface, click/tap the 3 dots below your post, click edit, remove the link to the image, reupload the new image by tapping the image icon in the post toolbar, select image, upload, voila!
As on how to edit the image, well use some image editor app on your phone? My Galaxy S23 has a default editor. Or just download the image I edited for you.
Oh, must be some lemmy.world shenanigan, it never happens on my instance. You should contact your instance admins.