Thomas did the rest of the work taking it into the end zone for a 72-yard touchdown that helped give the Saints a 10-point lead.
Horn was fined $30,000 when he pulled a similar stunt 15 years ago, but that was also his second violation of that season, according to ESPN.
The former Saints WR said he texted Thomas and "thanked him for doing what most athletes in his position would never do".
Horn played seven seasons in New Orleans, racking up record-setting franchise numbers at the time.
Thomas said the message on the sideline was about being smart at the end of a close game. Thomas hadn't talked to Horn about the celebration prior to the game. "We don't want to corrupt the game like that". Thomas held off his teammate and went to the field goal post pad.
Sunday was a flawless example of the power an attention-grabbing stunt can have as "Joe Horn" who last played an National Football League game in 2007 - was featured in more than 35,000 tweets less than an hour after the final whistle.
Thomas said he watched the celebration before the game and had been thinking about duplicating it for a while. All these guys just catching touchdowns and celebrating with each other, having fun, getting the crowd involved. Nope, that honor belongs to Joe Horn. who did the exact same thing as Thomas. "I felt had an opportunity to make it happen, put the game away and make the call".