What I do about the coins which are not on that list (besides cry). I have about 50 to 100 different types of coins, and some in very large quantity.
You could google - site:bitcointalk.org yourcoin and see if there's a thread on here for it. If it's alive then you'll know from that.
I don't know if coinmarketcap covers absolutely everything but it probably does.
Quite a few coins seem to attract a new developer and come back from the dead. Others may indeed be long gone.