(CNN) -- There was a dash of hope and a dose of disappointment in the search for an American family and their friends lost at sea for the past month.
New Zealand's Rescue Coordination Centre released an undelivered text message found in the satellite phone system used by the schooner Nina. It's the last known message sent from the ship.
The message sent on June 4, but never delivered, reads: "THANKS STORM SAILS SHREDDED LAST NIGHT, NOW BARE POLES. GOINING 4KT 310DEG WILL UPDATE COURSE INFO @ 6PM."
The transmission is important because it gives search teams the approximate location and actual time of the last transmission, said Nigel Clifford, Maritime New Zealand's general manager safety and response services. Information can be used to help rescue teams plot search areas.
The message was found in the system of the satellite phone provider, Iridium.
The ship went missing en route from New Zealand to Australia.
Even with the new information, authorities have not been able to find the ship. Six Americans and one Briton were on board.
"Today's radar search of more than 97,000 square nautical miles has been completed without any sighting of the vessel," the Rescue Coordination Centre said Thursday.
The Nina was built out of wood in 1928, but it's tough, said Cherie Martinez, whose brother, David Dyche, is the Nina's owner and its captain.
"Nina always comes back to port. She might get disabled, but she always comes back to port," Martinez said.
Martinez has faith in her brother's strong sailing abilities. Dyche has firmly handled the Nina's rudder on the high seas for decades. Twenty years ago, they crossed the Atlantic Ocean together.
The weather dealt Dyche and his schooner an ill-fated hand after they left the port of Opua in northern New Zealand, with his wife and their teenage son.
Four friends were sailing with them -- one from Britain, the other three from the United States.
Not far into their planned 1,200-mile tour across the Tasman Sea, the waters picked up fury. Evi Nemeth, a revered computer scientist, was among the crew. On June 3, she called a meteorologist by satellite phone.
She reported 60 mph winds and 18-foot waves and asked him for an escape route.
Head south, he told her. But brace for a storm.
The next day, he received text message: "ANY UPDATE 4 NINA?...EVI."
Dyche's mother did receive a fuzzy phone call that sounded like it was coming from overseas sometime after the seven crew members set sail.
She heard her name, then the line clicked out.
The tempest must have been a mean one.
"Records show that conditions at the last known position for the vessel, on 4 June, were very rough," Maritime New Zealand said. Winds of 50 mph with gusts of 70 mph had to have battered the 70-foot sailboat, while 26-foot waves tossed it around.
The Nina went incommunicado while running from raging seas, 400 miles north-northwest of New Zealand.
The sailing yacht is well-equipped, with a tracking device, a satellite phone and an emergency buoy, which is meant to deploy automatically when a ship takes on water.
But not a single signal has come from the boat for more than three weeks.
Family members alerted maritime authorities in New Zealand in mid-June that the Nina was missing after wondering for days why they had not heard anything from Dyche.
Rescuers put out a notice to all ships in the Tasman Sea, requesting reports on any sightings of the ship. None came in.
The search from the air began, and it continues.
"While we have grave concerns for the crew on board Nina, we have not given up hope of finding survivors," mission controller Neville Blakemore said.
CNN's Ben Brumfield and Miguel Marquez contributed to this report.