Tost had previously talked up a potential purchase, saying - amid admissions from Renault that they were evaluating how they might improve their F1 representation - that "to be owned by a manufacturer would be exactly [the] step forward the team needs to be established in the first five [in the championship]."
However, asked by Formula1.com about the current situation between the two parties - and Renault's rumoured shift in interest towards purchasing Lotus, the team they used to own - Tost admitted that the French firm now seemed to be looking elsewhere.
"I can only say what has happened in the last months in connection with Renault and Toro Rosso," he said. "Yes, they have visited us in Faenza and Bicester but in the last weeks it has been quiet, so I assume that they have decided to buy another team.
"How that would influence Toro Rosso we have to see. We have to wait for Renault's move and announcement. Then we have to discuss a programme that fits the requests and needs of Toro Rosso."
Renault currently supply power units to Toro Rosso and stable mates Red Bull, with Lotus having switched to Mercedes power ahead of the 2015 season.
Check back on Tuesday for the full exclusive interview with Franz Tost, including his thoughts on the proposed 2017 rule changes, Max Verstappen and Carlos Sainz's first half of the season, Toro Rosso's lower than expected championship position, and why the team are keen to retain technical director James Key in the future.