He would have given his statement to police most likely on July 1. The police have a record of his account, as does the DA, the defense, court filings, etc. There are sources galore other than his own mouth to a reporter's ear.
Also the girl, in telling her story to friends early on, (remember, the gag order was just issued), probably told them the story.
But I will say, that Luke Bray's account did say that she drove home alone. So he either didn't know the facts or the bellhop story is a load of bunk. However, it appears various media are doing independent verification, unlike the Bray account. Also, the way it was recounted in the article about Bray, it could be the reporter assuming because it is not a quote from him.