Horn, now 46, told Jeff Duncan of The Times-Picayune he was working out by himself in a gym in Mississippi when he witnessed Thomas' tribute.
"When I saw him bring out that cellphone, I teared up," Horn said. "That's something that some kids don't do, to pay homage to an old soul. For him to do it on a national stage took a lot of courage. I'm humbled."
Horn played seven seasons in New Orleans, racking up record-setting franchise numbers at the time. During his run with the Saints from 2000-2006, Horn blasted past the 1,000-yard barrier in four of his first five seasons, and was selected to four Pro Bowls. His franchise records for receiving TDs in a season (11), yards in a year (1,399) and career TDs (50) have all been bested.
Horn, however, still lays claim to the cell phone celebration.
Thomas said he watched the celebration before the game and had been thinking about duplicating it for a while.
"I loved the celebration," Thomas said. "I loved the swagger that he brought. I love how it got the crowd going. I definitely was thinking about it, but I'm happy I waited for that moment."
Horn's celebration on Sunday Night Football in 2003 drew a flag and a $30,000 fine from the league office. Thomas likewise was penalized on the play, and will likely see a fine coming his way as well.