Symptoms
Missing Sharepoint solutions in Sharepoint 2013 farm
Diagnoses
The solutions visible through central admin -> application management -> view farm solutions are the sharepoint 2010 integration artifacts, which are used for SP2013 sites run in SP2010 compatibility mode.
Resolution
The .wsp files deployed as part of the K2 Blackpearl install are not needed for SP2013 integration, unless 2010 compatibility mode is to be used.