Oh you were to fast

I edited my post and added the reference to /media/flash, which is the "internal storage". By the way, the obvious solution to import a sketch file without editing the sqlite database is the following
1. create a new scribble inside the scribble app and remember the name (e.g. scribble_1337)
2. after that remove the file /root/notes/scribble_1337.sketch
3. copy or move/rename the sketch file you like to import to /root/notes/scribble_1337.sketch
that's it. the thumbnail will refresh next time you open scribble_1337.