Emails can be lost
Yes emails can be lost in cyberspace. Some firewalls or security programs can simply block delivery with no NDR. Some go into SPAM folders configured to delete upon receipt. Some can configure their email servers to drop emails without an NDR. There are actually quite a few ways that an email can be lost, as you put it, in cyberspace. Your own mail server could have a problem delivering it, it stays in queue, the Server will retry for a set period of time and depending on the configuration by the Admin, can simply drop the email when all retries have failed, again with no NDR. To name just a few of the ways.
BTW NDR = Non Delivery Receipt.
Cheers
D