You said you went via contacts network. Is this not his contacts network?
Did you mean something else, as in LI itself is fruitless and to reach out directly to past colleagues?
Yes, correct. I went to my contacts, not only in LI. And he writes he PMed all of his ones, and it didn't work, which is surprising to me.
What if you're not the type to maintain relationships w/ former coworkers?
Anyone I once had the personal contact info of - which could now be stale - is also a contact on LI. It just seems like a less weird venue to hit up someone you haven't spoken to since you last worked some position. That's also been largely the case when old coworkers reach out to me.
The key thing is he did hit up what could be defined as his network and got nothing.