Yep you are in luck. Simply right click on your discrete YEAR(Date) pill on the Columns shelf and choose "Show Missing Values". This is a handy feature in scenarios like this one:
Mr. Lutton you have come through for me yet again. I know there are certain flags and settings in other setups that allow for showing Null values, I just didn't see anything associated with the reference line for that functionality. Obviously, I was looking in the wrong place
Thank you so much!