When the brutal tyranny, immorality and disrespect of the Banu Jurhum for the Baytullah surpassed all bounds, all the Arab tribes united to challenge them and bring an end to their transgressions. As a consequence, the Banu Jurhum were compelled to flee from Makkah Mukarramah. However, as they were departing from Makkah Mukarramah, they buried a number of relics of the Ka'bah in the well of Zam Zam. They thereafter filled it with sand until they brought it level to the ground in such a manner that no sign of the well could be detected.

After the evacuation of the Banu Jurhum, the Banu Ismaa‘eel returned to Makkah Mukarramah and settled down, but did not turn their attention to the well of Zam Zam. With the passage of time, not a single trace of the well remained and it fell into total oblivion.

(Extracted from Seeratul Mustafa 1/34)