Generating DB infos for attachments - cant see them in Media files

Hi, I'm transferring a custom CMS into Wordpress, and I got a bit of trouble with attachments images. My setup is following:

0. upload the files into uploads/1999/01 directory
1. create an attachment post in wp_posts tables linked to the file
2. add wp_postmeta "_wp_attached_file" and "_thumbnail_id"
3. regenerate the thumbnails (with the Regenerate Thumbnails plugin)

Right now, images are showing as a post thumbnails (both on the front end and backend editing the post). However, when I click to the Media, I can't see them. Why and how to fix it?