Daytionship
(n.) Daytionship - A friendship with another person which comes about through coincidence or vague mutual friends in which two people find a lot in common and enjoy each others company, but only for the day in which they meet. The combination of factors which caused them to spend time together cease to exist after they've parted, meaning that they will likely never see each other again.
Dude, where were you all yesterday man?" "This chick and I had a daytionship after the party the other night and I forgot the rest of the world even existed.