Why Wasn't Bob Trained In Shamanism?

When I read the chapters in Ragni's Library I only read that bob was trained in Assassination, Archery, Sourcery and being a warrior (idk the word for this) but not shamanism. I want to know why.

 

This is gonna sound lame but it's very likely that it's because the shaman class was added 6 years after bob's lore was created

 

firstly, yes, what fish said

canonically though it's probably because 1) slykaar is the only shaman he knew of and he wouldn't really want to be trained by slykaar and 2) by the time he finished with the other 4 classes he needed to go back to ragni even if he could've found a different shaman to train him