They didn't go into the number of ways packets can be lost inbetween the sender and receiver. In my experience it is generally some small corruption at some poi

They didn't go into the number of ways packets can be lost inbetween the sender and receiver. In my experience it is generally some small corruption at some point that causes the IP or ethernet checksum/CRC to fail and the packet gets dropped. It is extremely uncommon nowdays and generally due to failing hardware, buffers are by far the most common cause.