Gai Waterhouse, due to face stewards' inquiry over Rockabill's Spring Stakes withdrawal, was all smiles after Vaquera won the Tibbie Stakes at Newcastle on Thursday.

Stewards scratched Rockabill from Wednesday's Spring Stakes after the senior veterinarian for Racing NSW, Craig Suann, inspected the horse at the trainer's stable and found him to be lame.

Deputy chief steward Greg Rudolph spoke briefly with Waterhouse on Wednesday before he confirmed on Thursday an inquiry would be opened at Racing NSW headquarters on Friday.

Vaquera, having her first start since running third in the Queensland Oaks in June, finished wide out on the track to score in a blanket finish.

She arrived just in time for jockey Tommy Berry to beat the Kris Lees-trained Gold Epona with Cameo a close-up third.

The result was a blowout for punters with Vaquera starting at $21, Gold Epona unwanted at $101 and Cameo starting at $31.

The $3.70 favourite Lilliburlero finished sixth.

It was in March that Vaquera won her maiden at Newcastle.

"Isn't it amazing how things work out," Waterhouse said. "From winning a maiden here to running third in an Oaks four months later.

"She is a very promising stayer and although today's race was 1400 metres it was more like a mile because of the wind.

"This race was crucial as a stepping stone for her.

"We will keep her in Sydney for the time being then look at taking her to Melbourne."