You know it's funny now that you mention it, I don't know that this has actually come up. The characters that were taking warcaster were either clerics n paladins, so I reasoned they could touch their focus with their weapon hand when they had warcaster (since they can do the somatics with it). The arcane martials that didn't take the feat just sheathed their weapons that turn and drew them the next, or they had pact weapon and called it to them with a BA; the ones that did take the feat never cast spells with material components.
I guess I'm not as much of a hardass as I thought, 'cuz I'd be tempted to say that if you take warcaster, as long as it's a non-costly component, you can go ahead and cast S+M with that weapon hand. Costly components though, sheathe/drop that weapon.