Bramhastra has a tightest grip than any other grip in the world. But foolish Rakshasas thinking Hanuman would escape tried to bind him through ropes and clothes. Seeing this dishonor bramhastra went back to Bramha loka. Bramhastra usually is troublesome to Shiva and others too,but it did not trouble Hanuman ,yet Hanuman acted as if he was caught by it, Bramhastra acted as if it had troubled Hanuman , but Rakshasas since disbelieved its effect ,it disappeared.
Those who disbelieve Bramha tatva and Hanuman tatva and take shelter of other tatvas , the real Lord's (Bramha) shastra leaves them away immediately ,they are all fools.
Valmiki also makes it a point that Bramhastra did not have any effect on Hanuman.Since Hanuman is Bhavi Bramha ,bramhastra cannot have effect on him.From that day Bramhastra could not be reused by Indrajit. Once you use weapons on your elders , you lose that capability of using weapons again. your valor also diminishes.
Ravana asked Hanuman , " monkey who are you? who is your master?"
For all rakshasas even after so much of disaster , Hanuman remained only a monkey proves that they were fools beyond comprehension,and Ravana their leader/king was also a fool there need not be a special mention.
Hanuman ,after praying sri Ram ,said, " Do know me as the strongest ,bravest ,vayuputra a messenger for Sri Ram and For you I am very yama the Death ".