Help Map file problem

[nkmol]

my friend got this problem too. He can see the .map file in the Level editor, but when he wants to search for it in the direction he saved it. He can't see it. I though it was a hidden file, so i setted the setting to Show hidden files/maps. but no positief resolts.
I couldn't find a solution, so i gave him a empty .map file where he can work on. That works fine for him.
I don't know a other solution, sorry