Facemate
A facemate is someone who uses Facebook to flirt with exes or people they wish they had dated. They're just sad and lonely.
My facemate messaged my ex. He said 'Hey, remember me? I was kind of cute.'
My facemate asked my ex out. She said 'No, but I remember you.'
My facemate is still flirting with my ex. He's been doing it for 10 years.