Beaglebone DCAN BUS-OFF without Transceiver

Hi,
I have a few questions about the dcan port on the beaglebone or the am335x

I have noticed the following behavior:
If I activate the device can0 with ip link set can0 up type can bitrate 1000000 triple-sampling on, 
thus excluding loopback mode with no transceiver being connected, immediately after the writing of bytes can0
switches to the mode "Bus Off".

However, if I activate loopback "ip link set can0 up type can bitrate 1000000 triple-sampling on loopback on", I can measure signals on tx even
without transceiver.

Question 1: As I understand it, loopback mode simply means that the sending
device additionally receives their own data and not exclusively. is this
correct?
If so, is this the reason why it does not go into the "bus-off" mode here?

Question 2: Why is the device without a transceiver in "bus-off". How does
the controller in the AM335x know about the presence of a transceiver?

Thanks in advance,

Dennis