It's a made up word. A mix of "unbelievable" and "fucking" spelled as "fuhqing" since it looks less harsh and is pronounced the same as the word "fuck". Together it yields "unbefuhqinglievable".

It’s an acronym standing for Can’t Remember A Fucking Thing. It’s usually used to describe embarrassment at being unable to remember someone (CRAFT moment); going onstage as the lead in the latest theatrical performance and your mind goes completely blank (CRAFT situation); the next morning after a night when you got pissed as a fart and woke up in bed cuddling a traffic cone and a string of fairy lights wound round your prick.