The pair had met online and exchanged details in October 2011, and in March this year they met for the first time when she visited Sinclair and stayed at his Wanganui home.
One evening when the woman went to bed early, Sinclair sought out her wallet in the lounge and recorded her credit card details.
She returned home from her stay none the wiser, until her called her bank a few days later to say her card was overdrawn by $342, from her last purchase - an Air New Zealand flight.
Knowing she did not make the purchase, she cancelled the card and called Sinclair, who admitted using her card and told her he would pay her back. She went to the police.
Sinclair told authorities he had used the card to purchase a flight for another female friend to visit him from Auckland. He said the card's owner had given him her details in case of an emergency.
Mr Ross told the court Sinclair maintained he had been given the card details, but accepted it was not to fly in another woman.
Sinclair remains in custody awaiting next week's sentencing.
