But on Monday, a spokesman for UMC Quick Care told Fox News they never heard about Campos' supposed visit.
Mr Campos was due to give an interview last week on TV but reportedly left minutes before he was due to face the cameras for a medical appointment.
David Hickey, president of the Security, Police and Fire Professionals of America union that represents the security guards at Mandalay Bay, previously told the Los Angeles Times that he was attending a meeting with MGM representatives in one room of the suite as Campos waited with a security guard - hired by MGM - and another union member in the living room.
Mandalay Bay maintenance worker Stephen Schuck described last week on NBC's Today show seeing Campos in the hallway while both were pinned down by gunfire. Authorities have since changed the timeline again, saying Campos was not shot beforehand but was shot around the time Paddock opened fire on festival goers.
The interviews were canceled and the head of his union had been unable to get in contact with him.
Campos laid out his recollection of the incidents leading up to Paddock firing on a crowd at a country music festival across the street from the Mandalay Bay Resort and Casino on October 1.
According to witnesses, the security guard is no longer on Campos' property and hasn't been seen in several days. Police initially said Paddock had shot Campos through the hotel room's door during the attack.
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Police and the Federal Bureau of Investigation have yet to identify Paddock's motive, despite hundreds of interviews - including with Campos; Paddock's girlfriend, Marilou Danley, who was in the Philippines at the time of the shooting; and with Paddock's brother, Eric Paddock, who lives in Florida.
The former security guard, who worked there in the early 2000s, questioned Lombardo's statement that Campos was investigating the open door alarm. "Take cover!' If he yelled a second too late, I would have been shot".
The next day Mr Hickey said a union member informed him he was with Mr Campos at a walk-in health clinic but he didn't know the exact location.
Drapes billow out of broken windows at the Mandalay Bay resort and casino on the Las Vegas Strip, following a deadly shooting at a music festival in Las Vegas. A union leader, who was at the hotel with Campos at the time, says he hasn't heard from the security guard since.
LawNewz.com reached out to Las Vegas Metropolitan Police for further information.
The company that owns the Mandalay Bay Resort and Casino issued a statement Tuesday that implied it was in touch with Campos as questions mounted over the Las Vegas casino's response to the mass shooting. When police eventually breached the doorway to Paddock's suite, he was found dead of an apparently self-inflicted gunshot. Las Vegas Police told the site that the guard is not missing and that they know his whereabouts.