Thanks for the offer but I haven't yet made this instance available outside the local network. I'm still testing.
I did confirm through phpmyadmin that the rows are really being removed from the database when I cancel from the log entry screen.
Upon a little more digging I found the cancel button code is calling deleteTempQSO.php which includes the following in the where clause: $db->where('ID',-1);
* @author Howard Nurse W6HN
* This routine deletes all or selected contacts from the logbook
* It must live in the programs folder
$db = new MysqliDb("localhost", $sql_log_username, $sql_log_password, $sql_log_database);
die("Connection failed: ".mysqli_connect_error());
Looking at the entries in my Station.Logbook table, they all have an id of -1.