Unless you are allowing Nickel to run so the books gets imported after calibre has sent them, they will not be in the database and will not show on the next connect.
A couple of questions:
Where in main memory are you sending the books? I would suggest a directory with the books stored in subdirectories below that directory. This is most easily done from the Save template on the first page of the driver configuration dialog.
My personal choice is:
Code:
Elib/{author_sort:sublist(0,1,&)}/{title} - {authors:sublist(0,1,&)}
Elib is the directory in the root of the exposed storage, a subdirectory based on the first author in the author sort list is next and then the title - first author in the author list for the filename. The first item bits are to keep the number of characters in the file path/filename under control.
Elib/Carroll, Lewis/Alice's Adventures in Wonderland - Lewis Carroll.epub
Is the directory you are sending the books to visible to Nickel? If you installed KOReader using the install script or manually added the ExcludeSyncFolders= setting, it will exclude .adds and it's subdirectories.
Code:
ExcludeSyncFolders=(\\.(?!kobo|adobe).+|([^.][^/]*/)+\\..+)
When you safely eject and Nickel runs, do you see the importing content screen?