Drag and Drop symbols in Library

Hi everyone,
i have got a problem with actionscripting.That is i created 3 tab buttons and each tab buttons has got its symbols.I want to drag and drop them onto the canvas ,using drag and drop,but however when i click the second tab button the first symbol that i drag to the stage dissapears?Anyone knows how to make it stay .Is like a Signage developer for LTA(Land Transport Authority) Designer.

Anyway if u want the flash file for reference i can send it to u just leave your email.Thanks !