Hello, If you plug the unit back to power, observe if it would still cool perfectly. If it does, then it is not the refrigerant gas. If the unit would not cool down any more, then it is the refrigerant gas that had leaked out.
If it is cooling perfectly, try to find the drain pan at the back of the unit or underneath the unit. If this is filled with anything but water, you could expect some smell coming from that area and it could be filling the whole room which you can smell as if it is coming from the inside of the unit.