Bartra made a social media plea to track down the female fan, promising to gift her his matchday shirt if a meeting could be facilitated.
The lone woman was pictured wearing the yellow of BVB among a sea of Schalke's royal blue somewhere in the Veltins-Arena as the region's two biggest clubs played out a 1-1 Bundesliga draw.
Bartra's mission to find the mystery follower and reward her for a very public display of loyalty was launched on Sunday and reached a successful conclusion within 24 hours.
Yesss!! Thanks to everybody: fans, media... all of you! We've found our brave supporter! A promise is a promise, see you soon Steffi! pic.twitter.com/Cl2aXvWhGJ— Marc Bartra (@MarcBartra) April 3, 2017
The former Barcelona centre-back is clearly ecstatic the fan, who appears to be called Steffi, has been found, vowing to fulfil his promise.