If you decide the sex is the more important thing, enjoy it. This has happened to me a number of times and I think it is jut plain rude. Angry Dear Angry Sweetheart, how many times do I have to say it. All men are pigs. Look, if you want to meet someone just to get laid, don't expect them to remember you.
Some guys think a romp in the hay is little more formal than a casual handshake.
If you want to be remembered you have to present more of yourself than that thing between your legs. Try some conversation after you crawl out of bed. Exchange phone numbers. Arrange to meet for a coffee. If they aren't interested, consider yourself either a very bad lay, or just another notch on his bedpost.