Erasmus netted for the side on the final day of the French season on Saturday, but it was not enough to help them to promotion as they suffered an agonising late blow.
A 96th minute winner by Emmanuel Bourgaud for Amiens saw them defeat Reims 2-1 and shoot above Lens, who will now spend another season in Ligue 2.
There had been talk that Erasmus could make his move permanent, but it appears as though he will return to parent club Stade Rennes.
“I would like to say a big thank you to Lens for giving me the opportunity to wear the famous blood and gold shirt,” Erasmus wrote on his Instagram account. “I enjoyed every minute of my time at the club. Thanks to our amazing supporters for your amazing support, it was always special to play at the Bollard in front of a full stadium.
“I’m disappointed we could [not] win promotion because I believe a big club like Lens deserves to play at the highest level with our amazing supporters. Next season is another opportunity to make that possible.
“Thanks to the president, coaching staff and all members involved at the club for believing in me to be part of this amazing club.”
Erasmus made seven starts and six substitute appearances for Lens, with his final day goal the only one he scored, though he was used mostly on the wing or in a playmaking role.