Zac Brown -- Caught Up in Hotel Drug Bust

Country music superstar Zac Brown got caught up in the middle of a South Florida drug bust where 4 people got popped for cocaine and weed ... but Zac not only walked, the cops made it seem he was never there.

The bust went down last Friday at around 5:30 AM at the Four Seasons in Palm Beach. According to the police report, cops got a call to check out a suspicious vehicle in front of the hotel ... and ended up arresting a man in the car for possession of more than 30 grams of coke.

The man in the car told cops he had come there with 2 women, who went up to one of the rooms. Police were suspicious enough that they went upstairs to check it out.

Officers found 9 people partying. A guy was arrested for pot and 2 women got popped for cocaine.

Our sources say Zac was in the room and questioned by police. We're also told he was in possession of prescription pills, and cops asked him to send them proof it was a legitimate doctor's Rx.

Here's the mystery ... we have called the Palm Beach PD numerous times over the last few days to ask about Zac and all they would say is that he wasn't mentioned in the police report. We noted the police report said there were 9 people in the room, and it went on to break it down ... 3 men and 5 women. We noted the number didn't add up, so who was the missing person? They wouldn't say.

Now it appears Zac's name was on one of the documents .... yet they told us repeatedly Zac was not mentioned in any portion of the police report.

As for Zac, we have talked to his publicist numerous times about our story and she had no comment. In the last communication, after we outlined our story, she wrote back, "Didn't get [from Zac or the team] anything to add."