if you drop a weapon a and move your soldiers in order to don't look at it anymore, at next turn, the weapon disappears. That's ok. But if you look back at it, they are no more re-drawn, and thus become unvisible. if you remember were the weapons was, you can still pick it up.
Linux hp 2.6.32-24-generic #41-Ubuntu SMP Thu Aug 19 01:12:52 UTC 2010 i686 GNU/Linux
VGA compatible controller: ATI Technologies Inc M92 [Mobility Radeon HD 4500 Series]