I inadvertently hit the mag release on my PM9 at the range last week, and the fully loaded mag fell straight onto the concrete pad. The magazine did not come apart, but a couple of rounds came out of it. The result was a very slight beauty mark on the base plate.
I have never done this before, and it was obviously my fault, but no real damage occurred.
Your magazine must have hit on the corner of the baseplate, and the force was enough to dislodge it from the tabs. Did it re-assemble, and function OK?