Megatron DOTM repair help

Hi
Got the Megatron Voyager class toy from DOTM (the one with the rubbery cape) yesterday. Today, a wheel on his rear left side has come off. it appears that the screw that held it on has unscrewed. Unfortunalty the screw has no slot to hold a screwdiver (probs to prevent kids from unscrewing it) Does anyone have any advice on how I can fix this? I know he's supposed to be all injured but missing a wheel is too much for me :p
Thanks
Got the Megatron Voyager class toy from DOTM (the one with the rubbery cape) yesterday. Today, a wheel on his rear left side has come off. it appears that the screw that held it on has unscrewed. Unfortunalty the screw has no slot to hold a screwdiver (probs to prevent kids from unscrewing it) Does anyone have any advice on how I can fix this? I know he's supposed to be all injured but missing a wheel is too much for me :p
Thanks