well it's the same old rule, as old as the world is: do nothing.
don't call, don't text, don't email. if you feel hurt which is normal, since it looks like you wanted something more with him, focus on something else.
and just think: even though it might hurt a lot and seem like a tragedy now, you just wrote you knew him for about a week. meaning that you're suffering over someone who's been there just a WEEK out of your entire life. now, how can a person gain such an importance in just a week? ok, love can strike when you least expect it, but just stop for a second and think about WHO is he really.
How much of that "HIM" is really what he is and how much is your own vision, hope and projection of who he should be.
really, how well do you know HIM? how can you be in love with somebody truly without even knowing him? it is true that sometimes you can just "feel" a person and who he/she is, sometimes you can have this empathy and a gut feeling, but usually when these are around the guys don't run off after having sex with you for one time only.