Jack Cashill alert.
No, they would not. PETN leaves a very distinctive chemical signature. Discovering that that was the cause of the explosion would not have been difficult.
“Discovering that that was the cause of the explosion would not have been difficult.”
I don’t think that’s what the poster meant.
Perhaps the correct question is what would the official public version be.
At least two US airliners have been brought down in very similar circumstances.