My guess is because the image didn’t exist in other archives and it’s a very obscure site so why would someone have seen that? More probable they stumbled on something random like this in the wild or on Internet Archive?
Honestly, both options (website or archive) sound pretty unlikely to me. I'm wondering if instead it was a third option: maybe the originator of the copypasta was the person who originally took the photo. It would make sense for them to remember the event and go pull a good image out of their photo folder.
And "collecting" it. EG, saving it.
Some people will stare at live ants for hours, others collect rocks. I can imagine a person out of billions, liking "weird, musty rooms" or some such.
But who knows, heh.