Answer:
He wasn't sure what really happened.
Step-by-step explanation:
Walter Lord was among those involved in the wreck of a large ship known as Titanic.
It was made known that, the six lookouts, that was the people monitoring the movement and watching the route the ship was following, did not known that the side of the ship had hit the iceberg because they saw that the front of the ship was okay.
This did not make them to raise the alarm until the ship was beginning to sink.
That was why also, Walter Lord was reluctant or delay to add the quotation to his account.