Unfortunately this is one of the many disadvantages of the internet. People can disappear out of ones life for all sorts of valid reasons! Some go out if business, some retire, some even become seriously ill and worse still some even pass away and in this case we have no way of knowing?
I myself have lost contact with lovely people I have befriended all over the world from different interests etc. I know some of these are deceased and there would have been nobody outside their contact to inform me? An example was an 87 year old I knew from the lung cancer forum and not receiving news in nearly 15 years gives me one conclusion as our last conversation was a very nice and memorable one!