Why did Lehi's sons fail at first to get the Brass Plates?

Q: Why did Lehi's sons fail at first to get the Brass Plates?

A: Although all four of Lehi's sons made the long trip back to Jerusalem, it appears they didn't enlist the Lord's help directly. They knew where Laban lived, and cast lots to see on whom would fall the burden of asking him for the plates. When this first attempt fell flat on its face, Laman and Lemuel wanted to give up, but Nephi talked them into a second, stronger approach: to trade the riches their father left behind at their house for the Brass Plates.

This time, all four brothers went into Laban's house and laid out their massive wealth in front of him. They offered it all to him for the plates, and they did so in good faith. However, this is where Laban's true character came to the forefront. He proved himself greedy and murderous, first by kicking them out of his house carrying all their heavy stuff, and second by ordering his servants to chase and kill them so he could get it. Luckily the brothers outran their attackers, but only by dropping all their valuables, sprinting away, and hiding in a cave.

Why hadn't their attempts to get the plates worked? After all, wasn't it the Lord that told them to get them, and wasn't He supposed to help them? Again, it appears that, although they had made a valiant effort on their second attempt, they still hadn't asked Him directly for help and inspiration on how to get the plates successfully. This was a crucial omission on their part. However, because He's a merciful Being, the Lord would soon come to their aid.