Lol! Yes, Smithenhals, it's funny how that often seems to happen!
Sometimes not, however. And sometimes those who don't know any existing Brethren also don't know how else to get in touch and join. The old-fashioned strict version of non-solicitation can be very unhelpful in that case.
For example, I recall an old boy who was Secretary when I was initiated: his father was a Mason and had told him as a young man that he'd propose him when he reached 21, but then his father died unexpectedly and he knew no-one else (so far as he was aware) who was a Brother. He didn't realise that he was expected to ask to join - like a lot of people in those days (and some people even now), he assumed the opposite: that he had to wait for a Brother to invite him. So nothing happened for years and years, but eventually he joined through a work-colleague when he was about 50. Then, he was stunned to discover that half his family (uncles, cousins, etc.) were Brethren! But because he had never asked them, they had all assumed that he wasn't interested and hadn't said anything to him, and were very surprised when it turned out that for all those years he had been wanting to join but never knew how. He loved the Craft once he'd finally found his way in, and became a very dedicated Mason, but he always deeply regretted the lost decades and forever remained rather upset that his own family had assumed that he wasn't interested and had said nothing to him about it. Very sad.
Perhaps nowadays, with more openness from the Craft and so much information available on the Web, such cases will no longer arise. I hope.
T & F,
Huw