Yep I get that, as a Christian it's easy to go along with this.
However, most people that asked me the above question are atheists. So I had to try and come up with a plausible explanation for why he would not make himself known explicitly without going all Christiany on them. Also I had to try and come up with something that will make them think critically, and to somehow help them to reach the logical conclusion that the existence of God is plausible without being pushy or offensive.
Also the answer had to be concise and without being whiny, bang bang bang, and way you go type answers. I didn't want to waffle on.
Anyway if you can come up with something more logical, concise and persuasive, I'd be interested to hear it. That goes for both of the original questions BTW.
I'm gonna give this idea a spin for a while, and get back with some different approaches.