Unforgotten has risen to prominence again after shrugging off cardiac arrhythmia to snatch a narrow victory in the Group Two Phar Lap Stakes at Rosehill.

The Chris Waller-trained three-year-old filly is back on track for a tilt at the ATC Australian Oaks after she was only confirmed to run in the Phar Lap Stakes on race day.

Unforgotten had to pass a barrier test on Thursday after cardiac arrhythmia was detected once she finished last in the Group One Surround Stakes (1400m) at Randwick on March 3.

She had a soft trial, trailing the winner by four lengths, but had plenty on reserve when it mattered most over 1500m.

Unforgotten ($9.50) stormed home late under Jason Collett to pip Holy Smoke ($5.50) by a short head.

Hiyaam ($13) was 2-3/4 lengths back in third.

Waller applauded Racing NSW stewards for allowing Unforgotten to trial after acceptances.

"Making her trial is good from the punters perspective. Obviously there's a lot of questions that don't get answered in racing," he said.

"There will be a bit of criticism, I'm sure, but we're doing the right thing by the horse and as a result she's won a good race.

"We rode her quiet and let her finish off, that's how she won her races in the summer, where she was starting to build that reputation."

Waller felt cardiac arrhythmia was a stress-related issue.