As I understand it, Mudcat works on 4 search engines - these have been given names to avoid confusion
shorty, loki, dharma, and ragtime - during the recent changes some of them have been taken out of service for short periods
Supersearch ( which searches the DT ) is run on Shorty (I think)so if you searched while Shorty was off line you would not get a result .... it's just one of those things