I have a few fields in one of my content types that will not always have values entered for them. One such field is "Booking Contact." When content is created, if the author does not know the booking contact, then they are supposed to leave the field blank. However, this means that the field data is empty, and the field does not display in the node at all. I'd like to display a message for these empty fields-- similar to Views' no results text -- so that users can see that there is not a value assigned to the field. What would be the best way to go about doing this?
EDIT: I'd like to avoid using "default value" to define this. The message I want displayed doesn't make as much sense in the creation form, and will likely be confusing to users. Unless, of course, there's a way to hide the default value in the creation form.