The event had been removed from the Calendar of Events on their web site, so I called the library up today. It's officially been CANCELLED.
The library associate I talked to read me the press release of the cancellation (which has not been put up on the web site yet). It said that the event was cancelled due to unforeseen circumstances and they hope to reschedule later this year.
However, the associate I talked to was very nice and went digging for more information for me. She found out that Dave had to cancel because of shoulder surgery.
So I know all of us here are wishing Dave the best and a speedy recovery and hope everything goes well for him.