Closure not recognisable, the safety duty may persist.
If the closure was not clearly recognisable, the operator slope safety duty may persist. Anyone skiing a seemingly open slope may rely on the usual safety measures. Whether the marking was adequate is a question of the individual case and the evidence. Photos of the access and the signage are central here.
Next steps: photograph the access, the signage and the visibility and snow conditions, secure witnesses and have the safety situation assessed by a lawyer.