Well in the case presented, since when she got to the dealership oil was still in the engine, there is no way the oil pan was stripped before the service, as oil would immediately leave the engine without the drain bolt.

It doesn't really matter if someone else worked on it or not. It would be highly unlikely the engine would still be running without oil, and the dealer would immediately tell her she came with no oil in the engine, not that her oil pan is stripped.