Demons without publicised sigils

[VioletSatori]

A month ago or so, I put energy into finding my Guardian demon and I think I have found them. However, their sigil isn't on the "Demon list" and I have no idea how can I contact them without it (I just now got the opportunity to preform my first summoning).
What could I do? Concentrate on their appearance as described on the page? Should I postpone any rituals and work extremely hard on clairvoyance -audience?

Thank you in advance.