The Orlando Sentinel's Scott Powers was the only journalist assigned to the $500-a-plate event on Wednesday.
Biden staffers kept him away from guests by putting him in a storage closet and posting a guard to ensure he couldn't get out. Powers was in there for about 75 minutes.
"I kept opening the door and peeking out there to see what I could see, and I kept being told, 'Go back inside, we'll let you know when you can come out,'" Powers told ABC News.
Biden's staff has apologized for the incident.
"Scott - You have our sincere apologies for the lack of a better hold room today," wrote Elizabeth Alexander, a spokeswoman for Vice President Biden.