Summary: a short walk up Hargrave Creek from the beach lagoon and through a short section of forest to Lawrence Hargrave Drive. 15 minutes or so.
Directions: park at Stanwell Park Beach Reserve. Walk down to the beach and then to the northern side of the Hargrave Creek lagoon. Follow a sandy track alongside the creek back inland. Cross back to the southern side at a small pedestrian bridge. Continue alongside the creek through the beach reserve. Just after some picnic shelters turn right back across to the northern side of the creek on another pedestrian bridge. The creek is forested here. Follow the bush trail up to Park Parade. Turn left and proceed for 80 metres or so along the road until a small track is discerned on the right heading up more steeply through the bush. A mesh fence prevents entry to the creek on the right. Continue up to Lawrence Hargrave Drive.
Point of disappearance: Lawrence Hargrave Drive runs directly across the old creek ravine, which has now been filled and replaced by drainage pipes. It would be possible to continue across Lawrence Hargrave Drive and re-find the creek, but it is essentially lost for me as it passes deeply beneath the road.