Hi everyone,
how can i know that a coin is "dead" ?
Definitively, when all the nodes are gone.
However, as cryptorob mentioned above, an MIA dev is a huge red flag!
Nevertheless, it is worth remembering that the dead sometimes has a way of coming back to life.
So if you are holding a substantial amount of Legit (hey, hey!), hold on to it for a couple of months, just in case someone intends to revive the project.