If the license is on the USB eLicenser, it can not be sent. It has to be transferred, and therefore the USB key holding the license and the USB key receiving the license need to be connected to the same computer.
If this activation code had been used already, it is useless.
Yes. He needs to de-register the license in his MySteinberg Account, so you can register it to your account. And he must send you a USB key with the license on it.