The 30-year-old Snowsill had been scheduled to race for the first time this season at the World Cup race at Mooloolaba in Queensland but a stomach complaint forced her to withdraw.
Compatriot Erin Densham, who finished 22nd in Beijing four years ago, subsequently won the event by almost a minute in two hours, three minutes and 32 seconds to put herself in the frame for one of Australia's three berths for the London Games.
Beijing bronze medallist and twice world champion Emma Moffatt has already been pre-selected for one of the spots while 20-year-old Emma Jackson put in a strong case for taking another with her win at the Oceania championships earlier this month.
Three-times world champion Snowsill is the most successful women in the short history of the sport but is now likely to have to impress during the Sydney leg of the elite World Series on April 14 to make her case for selection.
Densham, who underwent surgery on a heart defect three years ago, said she had not been thinking about a London berth and was just happy to showcase her talent.
"I wasn't giving them a message, I was just running my race and doing what I normally do, what I know I can do," she said in a news release.
"Whether that impresses them or not I don't know, but it's in their frame of mind now, I just did what I had to do."
The women's triathlon at the London Olympics will take place in Hyde Park on Aug. 4.