Lawson deputised for Ricciardo during the 2023 season when the Aussie star injured his hand, and impressed during a five-race spell, but the team ultimately decided to give Ricciardo the full-time contract for 2024.
However, the 35-year-old's performances throughout the season were poor, being largely outperformed by much-less experienced team-mate Yuki Tsunoda, leading to the Faenza-based outfit dropping Ricciardo for good.
Now, his former boss Horner has been reflecting on the Australian's career, with the fan favourite having spent the majority of his F1 life within the Red Bull family.
The Red Bull team principal admitted one regret he had from Ricciardo's time at Red Bull, where he claimed seven of his eight career victories, in a successful spell between 2014 and 2018.
"Daniel's a brilliant character and a brilliant human being," Horner told the F1 Nation podcast.
"He lights up a room when he walks into it he's got that infectious smile. We never did manage to do a toothpaste deal with him. We tried very hard.