Lyric discussion by daveyHORIZON 

Cover art for A Lot Like Vegas lyrics by Bring Me the Horizon

the song is about regret

if you recall back to the first album, This is What the Edge of Your Seat was Made For, they had a song titled Traitors Never Play Hangman, which was Oli's dark confession of how he was miserable with the fact that he had cheated on the girl he was with.

This i basicvally the same thing.

"what happens in vegas stays in vegas" its a saying

so all the gambling and vegas refrences has nothing to do with literal vegas.

its just the context in which it fits.

what he did, no one needs to know, aside from the people/persons there.