If you are using fossil, use

sdC0!9fat!9pccpuf

with the right file in 9fat.  I can find no ability in
9load to get a kernel from a fossil partition.  There
does still seem to be an ability to boot from a kfs
partition calles 'fs'.  9load does not seem to have
forgotten how to do that.

Perhaps the confusion is that we now use fossil as the
default file system and people are expecting 9load to
load kernels from it due to kfs instructions in the
wiki?

The wiki is always out of date.  As far as I can tell
it is a 'fire and forget' document.  Read it with a grain
of salt.