Actually in Devarim 1:22 the term ויחפרו is used. But as will be explained, Moses did not send out the 12 leaders for ויחפרו:
In the next verse, 1:23, see Rashi, he says Moses agreed to send out spies only in order for them to feel more comfortable about conquering the land, and he hoped they would change their mind when they saw that Moses was confident about conquering the land. But really he himself felt is was unnecessary because he was confident since God said they would get the land. But that's not what happened. They still wanted to spy.
At that point, he decided to consult with God, but he had something else in mind. He felt it would benefit the nation in another way. It would excite the Israelites to see the wonderful produce of the land "so they would ascend to it with great eagerness." (the quote is from Ramban beginning of Shelach). And by the by it may placate the nation, because it will seem to them that people are being sent to the land for the purpose they requested.
And this is what he was advised to do by God. This is why in Shelach God says send אנשים - "men" not מרגלים "spies", and why it says ויתורו - which can be translated as and they shall scan out or scour as opposed to the more intensive ויחפרו, to dig and excavate, that which should have remained hidden. This is also why the 12 leaders were sent out, because they knew the wants and interests of their specific tribe, and why all 12 of them went through the entire length of the land and they didn't split up, because no one knew yet where his personal tribe's portion laid, because the lottery was not yet performed. So they made sure to scout the entire land, including their own future portion. And everyone knew about this task, which is uncharacteristic of a spy mission.
On the other hand, by Joshua, who "sent out two men to spy secretly"- שנים אנשים מרגלים חרש. It was two regular men, not leaders of the nation. And only two- the more under the radar the better. And they were to be spies. They only ended up going to Jericho, because as soon as they heard from Rahab that their terror was upon the hearts of everyone in the land, and there was no more "courage in any man, because of you", 2:9-11,there was no more need to spy further.
From a talk of Rabbi Menachem Schneerson, Shelach 1991.