Don Phillips, who provided vocals on the pop diva's track 'I Will Still Love You' from her debut album Baby One More Time, was one of the many hopefuls at auditions in San Francisco, California this weekend.
Witnesses during the taping say Spears instantly recognised the singer, and was "emotional" as Phillips performed.
However, despite the heartfelt reunion the audition did not go smoothly, and the X Factor judges ruled against Phillips continuing on in the competition.
WENN reports that the aspiring performer has now taken to Facebook, slamming Spears and making fun of her previous bouts with mental health.
He wrote: "Back to real life… all my demons released… i totally crocked when the pressure was on… at least I didnt shave my head… my vocal chords tightened up like a snake around a mouse.
"A couple tears later… and I am standing tall… I am free and God is good. I know some people say I havent taken care of my vocals over the past ten years… but its funny my worst is there best… minus autotune… its all good (sic)."
The new season of The X Factor premieres this September.