Welcome and thanks for the generous offer. Unfortunately this is a pretty complex issue: the general rule on SWM is that every author has full control over his/hers stories and those who wish to go and continue them should get permission first.
Given that, it's true that many writers just disappeared at some point and their stories are just there waiting. If you, or anyone else, wish to write a continuation contacting the original author, or the SWM staff, should always be the first step.
(formerly Anon, still Librarian)
"What is the point of having free will if one cannot occasionally spit in the eye of destiny?" ("Gentleman" John Marcone)
The following user(s) said Thank You: shadar, kshoo