It works much the same as the misdirection used in a magic trick or a pickpocketing, where you realise that your watch or wallet is gone.
Curt: Really? What about Alex, you know, your new girlfriend?
Brad: Ahh yeah...I've obviously been so distracted by her that I never noticed how much I want Jen!
Curt: That is some unfortunate Misdirective Love because now you're stuck with Alex.