Olympics: Great Britain increase medal haul despite frustrating day
Great Britain took their medal tally to 57 on Day 14 of the London Olympics - but missed out on more gold.
And boxer Anthony Ogogo, the women's hockey team and taekwondo fighter Lutalo Muhammad also secured bronze.
But Britain, who won 47 medals at the 2008 Games in Beijing, were frustrated in several other events.
Beijing bronze medallist Stevenson, who has recently lost both her parents to terminal illness, had hoped to emulate Jade Jones, who won Britain's first taekwondo gold on Thursday.
But Stevenson, the 29-year-old world champion who has also recently overcome a knee injury, was beaten by America's Paige McPherson.
"The injury did not play a part today," Stevenson told BBC Sport. "It has been a mental fight every day for the last 18 months and I did my best."
Muhammad claimed GB's second taekwondo medal of the Games when he defeated Armenia's Arman Yeremyan in the under-80kgs category.
A controversial selection ahead of world number one Aaron Cook, the 21-year-old lost his opening contest but came back to win bronze.
"I knew I had to try to win a bronze medal for Team GB and it's very sweet now I have done it," he said.
Boxers Luke Campbell, Fred Evans and Anthony Joshua guaranteed themselves at least a silver by winning their semi-finals on Friday.
"It's all about the gold medal for me now, but I'm proud of what I've done so far," said Campbell.
Elsewhere, Tom Daley scraped into the semi-finals of the men's 10m platform event. With the top 18 divers qualifying, the 18-year-old Brit finished in 15th place.
Patience and Bithell were already assured of silver in Weymouth but could not overhaul the Australian crew of Mathew Belcher and Malcolm Page in the medal race on Friday, which had been postponed on Thursday because of low wind speeds.
Bithell told BBC Sport: "We got the better of them at the start and managed to sneak ahead, but we were kind of hoping the fleet would be there to help.
"They sailed a fantastic race. We tried to attack them when we could but they held their nerve and they're worthy champions."
Reacting to her silver medal, Mills said: "I am pretty gutted, to be honest, but we've had a wicked 18 months together. Sas is amazing and we've had a great time."
GB won bronze in the women's hockey by beating New Zealand 3-1 thanks to goals from Alex Danson, Crista Cullen and Sarah Thomas.
"I am going to have to work hard to hold it together," said an emotional GB coach Danny Kerry. "That is seven and a half years of my life, so there is just a deep contentment."
With 25 golds, Britain have already eclipsed their Beijing total of 19 and registered their best medal haul since the 1908 London Olympics.
There was some notable success for international athletes in the Olympic Stadium on Friday.
In the women's 4x100m relay, the United States broke a 27-year-old record to take gold, while Bahamas won the men's 4x400m for their first success of London 2012.
It was a night to savour for Turkey, too. They won gold and silver in the women's 1500m, Alsi Cakir Alptekin finishing ahead of Gamze Bulut.