For some reason, when opening up a saved Visio diagram that uses the BPMN stencils, these no longer show up in the Shapes window.
To get them back, click on
More Shapes > Open Stencil... then find the Visio content directory, in my case this is
C:\Program Files\Microsoft Office\Office14\Visio Content\1033, and then enter
BPMN*_M.vss to show only the metric BPMN stencils. Select them all, then click
I have no idea why it isn't stored with the document somehow. Apparently if you go to
File > Info > Properties > Advanced Properties and then check the
Save workspace option, then it should save things like this, but that's checked for me and it doesn't. Maybe because it's the Professional version and not the Premium version, but I doubt it. Sounds like a bug to me.