Horner was subject to a detailed probe by Red Bull's energy drinks company over allegations made against him by a female employee.
After a process that took eight weeks, and involved an independent barrister, the complaint against Horner was dismissed on Wednesday, and he was cleared of any wrongdoing.
But with Red Bull having offered almost no explanation for its findings, and making clear it will keep details of the matter private, there has been concern about things having been swept under the carpet.
Speaking at the F1 season opener in Bahrain, Mercedes boss Toto Wolff and McLaren CEO Zak Brown both called on F1's commercial rights holder and the FIA to take steps to ensure everything had been conducted properly.
Asked about Red Bull's findings from the investigation, Wolff said: "Well, I just read the statement, which was pretty basic.
"My personal opinion is we can't really look behind the curtain. At the end of the day there is a lady in an organisation that has spoken to HR and said there is an issue and it was investigated. And yesterday, the sport has received the message: 'It's all fine. We've looked at it.'
"I believe that with the aspiration as a global sport on such critical topics, it needs more transparency. And I wonder what the sport's position is?
Source: Autosport