They were probably filling in on those days. 
Mark Mancuso's relative disappearance is a big loss for TWC. He was never flashy, but always solid, and, like Rich Johnson, has a knack for giving you just enough science without being overwhelming.
I used to love to watch him Thur-Fri on Weather Ctr (usually paired with Kristin Dodd - if no fill-ins were needed) and on the weekends.
The best, though, was when he'd fill in for Kelly Cass on Day Planner on Thur-Fri. TWC had Kristin Dodd and Eboni Deon available as a female fill in on those days, but they'd usually pair Mark with Bill Keneely. Those two would put on a clinic on how to be a professional OCM. They were amazing together - two solid veterans, showing the newbies how to get it done. I remember watching them together in 05 or 06, just as TWC was hiring some pretty piss poor new talent and giving them prime slots (Kevin Robinson and Betty Davis, who both are still mediocre) or promoting other newer but not very good talent (see: Alexandra Steele) to prime-time. As I watched Mark and Bill work their shift together, I couldn't help but wonder why TWC didn't have them in better time slots.
