The youth was arrested on suspicion of murder between Thursday evening and Friday morning last week and taken to a west London police station.
The police are now appealing for anyone who saw or heard anything to come forward.
They say they are looking for three suspects described only as 'black'.
The incident happened around 9.30pm between the ground and third floor of a block of flats in St Dunstans Close in Hayes.
Father-of-three Mr Thrower, who worked as a handyman, died just before midnight on Thursday from a single stab wound to the heart.
Police and forensics were working on scene on Friday searching gardens in the surrounding area.
A public meeting is being held tonight in an attempt to combat residents' fears about gang culture at the estate.
The victim's brother, Darren Thrower, is expected to attend with his mother, Margaret Jackson, who lives in Larch Crescent in Hayes.
"This shouldn't have happened, that is what I am going to ask [the police]," said Darren.
"[Paul] phoned me worried.
"I thought it was just kids being stupid, but it wasn't."
The meeting is at The Crane Community Centre in Fuller Way and starts at 7pm.
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