If you are running an inquiry for blank retirement dates, you will find 0 students. The reason for that is that Maplewood does not change a student's status to Deleted without giving it a retirement date. The program looks for the status, Deleted, and not for the date field.
The 'no date' checkbox only works for when searching for students who have no date for 'Entry into elementary school' as this is the only field for which the program accepts no data.