The sloop Silver Heels, Capt. Eugene Nohl, returned to Vineyard Haven on Tuesday after spending more than two weeks in investigating the wreck of the rum runner John Dwight off Cuttyhunk and reported rather discouragingly that the hull is filled with bottles. Nohl, who has done most of the diving, said he had completed a thorough examination of the wreck, which he found damaged but slightly and sanded scarcely at all. But to the height of his shoulders, the entire cargo space is filled with empty beer bottles and rotted barrel staves.