Well, I have to add here...
It is far from rare occurrence.
I couldn't count the number of times I and others have carried out good and extensive research after a single query/post only to receive complete silence for a response.
I call them the 'post and run group ' and keep a list so I don't buy in too fast if there is another query from them
I have even on occasion PMed them saying 'hey there is information on your recent post"
Usually, further silence follows!
I would settle for just a one word response. "Thanks"
Sue