[TaSSaDaR]

For me it never failed to work. The weapon appears in the inventory. I probably know whats the issue in your case: when you make your mage cast the spell, don't switch to another character. Wait for him to finish it, and a choice panel should appear instead of main 'toolbar' in the bottom. You choose the type of weapon you wish to create (mace, long/short sword whatever else), then the weapon should appear. Make sure your mage has free inventory space.