The ruling on whoever doubts concerning the Stones falling into the Basin (at the foot of the Pillars)
Question :
What is the ruling on whoever has doubt that some of his stones did not fall into the basin?
Answer:
Whoever has doubt, then he must complete it. He should take some stones from the ground from where he is in Mina and complete the stoning with them..
Source:
Ash-Shaykh Ibn Baz
Fatawa Islamiyah, Vol. 4 Page 249