I've been working with a .mxd that has some broken links. I have been using the following python to print the workspace path for each layer:
>>> for lyr in arcpy.mapping.ListLayers(mxd):
... if lyr.supports("workspacePath"):
... source = lyr.workspacePath
... print "%s -> %s" % (lyr, source)
I found that layers do successfully get drawn and their data source is correct in arc map even if the workspacePath points to a .sde file that doesn't exist on the machine. If the links aren't broken, then there's no need to fix them; but I'm curious how ArcMap is able to find the data in sde if the layer workspacePath is not correct.