Dawood: per my understanding, verse 53:10 “So/thus he revealed (Wahi) to His salve, what he revealed (Wahi)” is a generic pointer to this Wahi/inspiration. It is in this extra ordinary encounter that prophet was informed of who is God, His plans to make him a prophet, etc.
Answer, again! The Quran states that it is the only revelation given to the Messenger. If Allah purified the salat that was handed down from Abraham, why did He not put this purified prayer ritual in a clear verse? Why leave it out when it is so important? I am not being unreasonable asking for a clear verse!
It could be claimed that every innovated practice in Islam not found in the Quran was from this 'hidden' revelation which is the claim of the hadith worshippers and the sufis who get extra knowledge this way or through their saints. By claiming extra revelation you do not have to quote from the hadith but the result is the same; number 2 islam.