There are a number of circumstances where ArcMap cannot find its data even if it is set to treat data location in the "relative" fashion. To fix this generally, one can go to Data/Repair data source on a layer's drop down menu. If one chooses "Select All" in the dialog box, one can fix (almost) all the layers at once. The catch is that it will not fix the link to any data set joined to the main source file in a layer. It tells you that, and actually doesn't fix it. But it does leave "tracks in the dust", so to speak; often the legend using the joined data and/or the actual symbology on the map is still there. However, the actual joined data is not on the attribute table nor recognized in the Properties/Symbology tab nor is there any record of what the original joined source was. Thus one has to set up the join all over again. There does not seem to be a way of finding out or verifying what the original setup was. I guess I was really surprised at this apparent situation.
Does anyone know how to recover the original join setup (if one doesn't know it) and repair the link to its data source?