What puzzles Bakha about his having had the courage to ask a sentry for the solar topee when he was a child, and why does it puzzle him?

Although as a child Bakha had the courage to ask one of the sentries if he could have the solar topee, now that he is an adult, he knows he will not have the courage to ask one of the Havildars, even though it is a better plan. He is unable to see how his experiences as he has grown older have made him a fearful person, and so this situation is confusing to him.