Thor i hope you will get back your map, i can assure you that a map with a dot somewhere in Europe is not something people easily take to make their own treasure story.
Being a metal detector idiot from the early days on ( been searching for more then 35 years on numerous battelfields in Europe) i can assure you your map will hardly be of any help.
To find an airplane that crashed is like finding a needle in a haystack, i have done my fair share of searching and only in a few times i could trace back a plane, even with pretty accurate Eyesight stories.
I can give you lots of places in Holland where i live with Eyesight crashsites where you will hardly find any trace of the crashed plane.
Your long time dream of finding it would be very very hard te realise.
It depends on the terrain, if its a wood or a rocky terrain then you would have a chance, on a field a plane with be hard to trace, the plane would be to deep to get.
I still hope you post here will have a happey ending