Mechelen were trailing Excel Mouscron 2-1 heading into injury time on Saturday evening, so Coosemans went up for the late set-piece.
The 25-year-old was the first to pick up his side's overcooked corner on the edge of the box, but failed to skilfully flick the ball past Jonathan Bolingi.
However, Coosemans' magical moment would come a few seconds later as his team-mate dispossessed Bolingi and the ball fell back to him.
Coosemans duly scuffed in a low ball towards 19-year-old defender Elias Cobbaut, who applied the finish to save a point.
Nobody was particularly fussed that Cobbaut scored, though – Mechelen players swarmed around Coosemans as the net-minder sprinted over to the touchline to enjoy his wild celebrations.
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