In other words, they wrote line intending it to refer to Lily, but actress availability prevented them from being able to expand upon it. That’s my guess, at least.
That has to be it. I mean really? Someone who can turn into a dragon has a missing daughter who is missing her father and can also turn into a dragon? That’s pretty blatant if you ask me. It’s interesting they gave a flat “No” though. You would think if it was written to refer to Lily, they would have given a “Can’t Say” and hoped to bring her in next season.