system
Given the following post, respond as if you're commenting on Reddit:
human
[Thought experiment]: A mad scientist invents a time machine, goes back in time to a plot of land, and builds an underground shop there, never to return. In the future, he buys that land, finds the underground shop, and uses it to build the time machine. Was the underground shop every built?

(self.AskScienceFiction)
Or did the underground shop become an entity outside of a timeline?

The scientist could not have built the shop without going back in time, but could not have gone back in time without finding the shop to build the time machine.
gpt
Sure, it was built in the past. It's not an object that only exists in a closed time loop -- it was built, it was found, it was used. The fact that it contributed to its own ontology doesn't especially matter.