updated 10/21/2012 AT 4:00 PM ET
•originally published 10/21/2012 AT 6:30 PM ET
On Thursday, the couple shared a romantic evening at Il Bolognese restaurant, but an unexpected outfit change left onlookers puzzled.
“The thing that struck me the most was that [Kim] came in dressed in one way and left the restaurant dressed in another,” the restaurant’s owner tells PEOPLE. “Mid-dinner [Kim and Kayne’s] driver came into the restaurant with a huge carrier bag and dress carrier.”
“[Kim] went into the bathroom and changed,” he adds. “Some of our guests were already quite stunned by her presence and even more so when she reappeared looking completely different.”
“When she came in, she was wearing a long black dress with long sleeves and a huge [slit] up the leg with knee-high boots but when then she left wearing a green outfit,” he says.
Kardashian identified the outfit on her blog on Friday. “I m wearing a green Lanvin dress and Tom Ford heels and accessories. I love this dress! I m really loving this deep emerald green color at the moment, what do you think?” she asked readers.
West, 35, and Kardashian started their meal off with parma ham and buffalo mozzarella, then paired pasta with Bolognese sauce and handmade tortellini stuffed with ricotta cheese and spinach with a bottle of classic Chianti red wine.
On Friday, Kardashian Tweeted, “Italy is so beautiful! Best birthday ever!!!”
Reporting by PRAXILLA TRABATONNI