I was able to cook on an induction stove with a non-magnetic pot, why?
It is likely that it was a different metal that supports inductive currents, such as aluminium. 

The problem with aluminium is not that it can't create inductive current and heat up. It can, but it is rather inefficient on induction. Also, it has a very low melting point, so with thin aluminium, you risk melting it. 

Many induction units have artificially added constraints to not work if they don't sense a ferromagnetic pan of a certain size, aswhich is a safety feature. Maybe yours doesn't, and so you were able to heat your pot. This doesn't make it a good idea to continue - even if you don't run into trouble with melting, you are losing much of the advantages of induction cooking.