פירוש על בבא מציעא 42:12

And why - if abandonment without awareness is not [considered] abandonment.

Given that - concerning the poor people from here, it is abandonment with awareness; since they saw the nemushot walked through it. But the poor of another city do not yet know - so how is it that we are permitted it. Rather it is because their abandonment, when they do know, is [considered] abandonment from the time [the nemushot] left it. So it was permissible when it came to the hand of this one.