The police did not know whether the thief knew what was in the envelope.
But he was not the same naive person the thief had once known.
There was little gold in his purse today, but a thief wouldn't know that.
Remember that the thieves must not know what you are doing!
How else would the thieves have known when we were to take the guns?
It looks as though the thieves knew exactly what they were going to take.
Given, a thief who has more money than he knows what to do with.
That is, the thieves would not know where, or when, the material was being shipped.
And the thieves, you know, who would have broke out under different leadership.