Jason, there's a podium at the front of the cafe. right at the edge of the back entrance lobby. Right behind that, there are columns and glass that blocks off the seated guests. The restaurant starts out fairly thin and rectangular shaped, before opening up into a gazebo type setting. Those guests waiting in the queue line, would physically have to enter the restaurant to accost someone sitting at a table. The closest table to the podium is probably about 25 feet away.
The more details you fill in, the more it appears that something was seriously wrong with this guy. To bypass the podium, enter a restaurant and start asking at tables who is a guest and who isn't, well, that goes way beyond rude and into the psycho category for me. I wouldn't be looking for hotel management to handle it at that point, I'd be calling the guys in the white coats. I'm sorry that these friends felt it was somehow the GF's fault or even took the guy at face value that he was even a guest there himself.
Guess these are good lessons that you're learning as you start down the road of hotel management. You'll be able to see things from both sides of the fence.