When you're attempting to avoid an average looking person, often after a drunken hookup, but said person looks so average that you think you see that person everywhere and every time you do you feel an irrational fear.
A: "Man what's wrong with you?"
B: "I just look into that crowd of people and thought I saw that girl I hooked up with last night like four times."
A: "Dude, shouldn't have hooked up with such an average girl. I told you you'd get bad tiphobia."