Idk if this should be called "There is no Scp" or "The file for an Scp that is the Scp" Theory: Deja vu is your brain misfiring the memory signal, so it makes you feel like it happened. I do also remember seeing a Minecraft skeleton turtle.
The lore is it randomly appeared in the foundation one day. That's it. Update from dev: Okay now it will provide possible answers to impossible questions, such as "What is Scp-055?"