From what I gleaned from the code, this warning is raised when an expected parameter defined in a particle does not exist in the record that has been given the particle.  At this point we are confident that the record is a valid record and contains at least one science parameter reported by this particle.  

If particles are considered optional then this seems like a good warning.  However, it would be good to be able to suppress warnings for parameters we explicitly call optional.  This is a compromise so we don't have to update the code or IDD.  What if we create a new ENUM with a list of parameters we have identified as explicitly optional.  If the key exists in that list then don't output the warning?  What do you think?