I’ve tried to look for this but apparently my Google skills aren’t what they should be. I remember reading a short story years ago that was set inside the Trojan horse, but you weren’t meant to know that from the beginning. It was part of the realization toward the end. I don’t remember the author but I think it’s one of those who are known for odd or surprise endings. Thanks for any suggestions.
Nathanael West’s first novel , BALSO SNELL, takes place inside the Trojan horse, I think, but it wasn’t very popular so I doubt that’s the story you’re remembering. If you don’t get any other answers, you could check it out and confirm what I’m saying.
C.S Lewis had an unfinished novel called “After Ten Years”, which was about the aftermath of the Trojan war. One of the published excerpts is apparently the first chapter and fits the OP’s description.