What happened to Brahmastra used by Lord Ram while traveling to Sri Lanka against the sea?

What happened to Brahmastra used by Lord Ram while traveling to Sri Lanka against the sea? When Shri Ram was ready to shoot it on ocean, then the lord of ocean appeared and apologized from him. And during the conversation he was still wielding brahmastra on the bow, in the end he asked what to do with the Astra from ocean lord as it can't be put down without using once it's wielded. So the ocean lord suggested that the present Thar reason, which was a water body in that era, is a home for a rakshasa and if Shri Ram diverted that Astra towards him then it'll be good and helpful for humankind. Afterwards, Shri Ram took his suggestion into consideration and shot it in that direction. That Astra didn't only kill that rakshasa, but also dried up that small water body and made it a desert.