Build Information files contain Version and Build information that is used for Execution Runs. They are are typically stored and searched for on the Execution Server; but can also reside on the Application Server, which is useful if you need to maintain a single Build Information file for all Execution Plans.
The reason why the Build and Version are not displayed in the Execution Plan Properties; is because the Build and Version are read from the file at the beginning of each Execution Plan Run. This behaviour is by design and documented in the SilkCentral Help Documentation.
If the Build Information is being read correctly, the expected Build and Version numbers can be see in the Execution Plan Results Details, as shown below: