True that... Sometimes I too observed that. Infact, yesterday night too!!!
Then I learnt that if "CAD file/s" are not uploaded properly or if they are not 'recognized'by GrabCad's system ( or by moderator !? ) then your files are not visible to others. Such message is displayed by GrabCad on upload of files.
After successful / complete upload.... Files are visible to all.
That's what I learned by my own experience yesterday night.
Regards,