"We messed up today. We are in good form at the moment but it feels like we have lost two points today. We can't be happy with one point," Weghorst told German broadcaster DAZN.
The draw is a missed opportunity for Wolfsburg, who would have leapfrogged RB Leipzig to go top of the table overnight with a win.
Yet a contested VAR decision and a late missed chance mean Wolfsburg now sit second between Leipzig and Bayern, who face each other in a blockbuster clash on Saturday.
Fortuna left-back Niko Giesselmann almost broke the roof of the net with a brilliant 16th minute opener, as he blasted the ball into the top corner from a wide angle to pick up his first ever Bundesliga goal.
The goal, ultimately given by VAR, sparked controversy as Wolfsburg protested that the ball had gone out at the touchline in the build up.
"We have this VAR, but the referee has to do his job. The ball went out," said Weghorst.
The Dutchman corrected the perceived injustice less than 15 minutes later, nutmegging goalkeeper Zackary Steffen at the end of a well-worked move to draw Wolfsburg level.
Felix Klaus came closest to grabbing a winner for Wolfsburg at the end of a turgid second half.
This weekend promises to be an early litmus test in the Bundesliga title race, as last season's top four teams go head to head in two highly anticipated clashes.
Borussia Dortmund host Bayer Leverkusen just hours before champions Bayern travel to league leaders Leipzig for the headline fixture on Saturday evening.