Mainland police this week said a Fairhaven man who disappeared from a Vineyard-bound voyage of the New England Fast Ferry late last month left a note for his family; as a result police now believe the man did not fall off the boat by accident.

On Sept. 24 Walter P. Tyler, 28, of Fairhaven, reportedly boarded the 1 p.m. high-speed passenger ferry from New Bedford to the Vineyard but never arrived on the Island. A team of investigators last week searched the waters between Buzzards Bay and Vineyard Sound but found nothing.

Last week, Fairhaven police chief Gary F. Souza said police were searching for a missing person, but he would not comment on whether Mr. Tyler left a note.

Earlier this week, Chief Souza said Mr. Tyler had in fact left a note with his family prior to boarding the fast ferry at the State Pier in New Bedford. The chief would not reveal the contents of the note, but said police have ruled out foul play in Mr. Tyler’s disappearance.

Chief Souza said police talked to a Pennsylvania man who was sailing aboard a 51-foot vessel out of Mattapoisett last Monday with two other men when he thought he saw a person slide over the starboard rail of the fast ferry into the water.

The witness told his friends what he saw and they steered the boat toward the wake of the fast ferry. They searched the area but found nothing except for a dark blue Fairhaven Father’s Road Race hat, which police later confirmed belonged to Mr. Tyler.

The group followed the ferry for 15 minutes without seeing anything else. Because the ferry did not stop or turn around, the witness began to think his eyes played tricks on him, and he and his friends gave up their search. After later hearing about the missing man, the witness realized that he had been right and contacted the Fairhaven police.

Mr. Tyler served in the U.S. Navy for four years after graduating high school and later joined the Merchant Marines where he worked on tugboats.