Non-van der Waals (n-vdW) 2D materials are gaining popularity due to their exciting confinement-enhanced properties for magnetic, catalytic and optoelectronic applications. The recent discovery of mechanical and liquid exfoliation of n-vdW materials along the cleavage planes, owing to the very low scission energies, is encouraging and opens the avenue for further exploration of n-vdW materials having exceptional properties. Herein, we successfully isolated a few layers of pyrrhotite (Fe7S8) nanosheets from bulk mineral ore by means of liquid phase exfoliation in organic solvent and studied the magnetic ordering at bulk and exfoliated samples. Both experimental and first principle theoretical investigations point out confinement-induced magneto-structural phase transition from ferromagnetic monoclinic (4M) to antiferromagnetic hexagonal (3T) characterized by the suppression of Besnus transition.