Hi Xymph,
this Map-UID is a
UUID or GUID (Microsoft), which is generated in this form in the game. The map UID is then generated from this UUID (and other profile data).
Until TMUF, only parts of the binary UUID were used. It would be impossible for it to be stored completely in the map.
During the development of Maniaplanet, however, the generation of the map UUID was simplified. The binary UUID is converted to a string and processed that way (I can't remember the details).
So I can't rule out that the game actually wrote this map UID this way due to a bug.
Another possibility is that the map UID has been changed (edited) by a player. With tools like
GBX.NET Exporer, which were developed on basis of
GBX.NET, Gbx files can be manipulated quite simply.
Using GbxExplorer I was able to write the UUID you mentioned above into another map without any problems. The tool does not seem to check the input for plausibility (at least not for the UID).