Great Britain's four-man bobsleigh team repeated their second run on Friday after GB2 driver Lee Johnston complained a stone had been thrown at him.
Johnston, a Royal Marine Commando, said the stone had smashed into his visor as he drove down the Utah Olympic Park track at more than 80mph.
"It was something that really scared me"
Johnston was visibly annoyed when he got out of the sled and Team GB officials immediately protested.
Johnston told BBC Radio Five Live: "I was coming out of bend 10 and all I saw was an arm come out in front of the bob and an object come towards me.
"It smacked me right in the middle of the visor, which completely blew my concentration - so much so that I nearly crashed in bend 13, I was off coming out of 14.
"It was something that really scared me."
The stone had been thrown onto the track by a child.
"They offered a re-run and GB2 accepted"
Both the child and its parents were taken away by the US authorities.
A spokesman for the British Olympic Association told BBC Sport Online: "The British team appealed to bobsleigh officials and after studying video evidence they accepted that an object had interfered with the British bobsleigh.
"They offered a re-run and GB2 accepted."
But the re-run was not as good as the first effort and GB2, which also included Philip Harries, David McCalla and Paul Attwood, slipped to 17th position.
GB1, driven by Neil Scarisbrick, were in 13th place after their two runs with a combined time of 1:34.14 - 0.88 off the lead.
The USA1 team were top after the first heat with a time of 46.65. And they increased their lead after the second run, a 0.09 advantage over Switzerland1 and Germany2.
There were two runs on Friday - or in GB2's case, three - with another two on Saturday to determine the Olympic winner.
At Nagano in 1998, Britain's only medal of the Games was a bronze in the four-man bobsleigh.