Not finding a LinkedIn page for someone can range from a neutral signal to a negative signal depending on the hiring manager. I personally don't read anything into it, but I know many hiring managers who feel that lack of a LinkedIn page is a negative sign. I don't like it, but it's how the world works some times.
A seasoned LinkedIn page is also becoming very valuable for applying to remote jobs. Remote employers are getting nervous with all of the overemployed people and fake applicants. Having a mature LinkedIn page with a decent number of connections to real people is a major positive sign for remote hiring.
It's not something you will be able to see or detect as a candidate.
