I asked this earlier question about whether there is a pumping lemma for DCFLs and it looks like the answer is "no."
If the answer were "yes," an authoritative answer might have the form "yes there is, and it's called X and looks like Y." However, I'm concerned that there is no authoritative way for someone to answer the question as "no, such a thing does not exist," since a justification of this answer couldn't just be "I've never seen one" or "I don't think so."
Is there a way for someone to authoritatively give a "no" answer to my question? If not, what should I do?