There are many reasons that a pitch can be declined, but the main reasons are:

  1. Another member has been selected for the project - this could be based on skills, experience or timing of the pitch (for example if she submitted her pitch before yours and was qualified).  
  2. You do not have the exact skills or necessary background for the job.
  3. The employer may cancel the project.

Do not be discouraged! This does not mean you are not qualified but in some instances employers are very particular and/or like to move very quickly. This does not mean another wonderful opportunity will not come along soon.  Good luck and happy pitching!