Great question! The reason that the Rank value does not display on your User Stories page is most likely because "Drag-and-Drop Ranking" is configured for your workspace.
If Drag-and-Drop Ranking is configured for your workspace, the Rank field is not displayed in the user story details. When Manual Ranking is configured for your workspace, the Rank value (numeric value) is displayed in the user story details.
Please take a look at the Rally Help page for Prioritizing Work (
https://help.rallydev.com/prioritizing-work" target="_blank) for more information.