Did you record it as DAO or as "appendable". I'm not sure how K3b works out when you leave it as "AUTO".
Probably if it was not burnt as DAO, closing the discs is not the same as Finalizing it.
Even after setting the links and mounting points through sys configuration K3b was not seeing my discs content, but I could see it in Konqueror.

About the way you burnt the disc, may I ask you was it a multisession, and the file(s) you want to see were not in the first session?
Sometimes this can be an issue, as further recording session risk to stay hidden.