The difficulty may be that it isn't something fixed that you could notate by starting at the beginning and copying each note as it was sung. In both the classical/operatic and folk contexts, singers have a repertoire of ornaments they use, and it it takes a lot of writing to get it all down: it also involves asking about the singer's intentions. In classical music you can find handbooks on how to ornament, which at least partially explain what an individual singer does - in the folk scene it isn't usually done that systematically, and the result is an edition of the song which supplements the core melody with pages of footnotes describing variant phrases.

In the extreme, a singer may have a particular ornament in their repertoire but choose not to use it in a particular performance. It's still in a sense present, and a complete transcription would describe it, but you can see why Creighton might have been puzzled about what to write down.