What type of map ? Overland ? Dungeon ? City ? Does it look like an Annual was used ?
That could narrow down places to look.
To help with this in future, you could do what I did in similar circumstances. When I made a village/town map for a certain area of my game planet, I saved all of those symbols in a fsc file with an appropriate name to it.
So next time I made a map for a village/town in that country, I just load that symbol set.
Also note that you can actually load an existing map into the symbol catalog window. Just hit the open symbol catalog button, in 'File name', type *.fcw and hit enter (this will cause the dialog to set the filter to now show map files instead of symbol catalog files), no browse to your map and select it, and voila, all the symbols from that map will now show up in the symbol catalog window.