A bargain-hunting day trip to Shenzhen turned out to be an expensive six-day lesson in mainland immigration law for a Hong Kong couple robbed of their passports and ID cards. Jonathan Gardner and Aiyada Kultakham thought a few hours of cross-border shopping at the Luo Hu Commercial City mall would be a good way to spend last Saturday afternoon. Everything was going to plan until Mr Gardner put his daypack down in a shop and turned his back. Seconds later, the bag was gone, along with his credit cards, a mobile phone and a camera. Worst of all, both their passports and Hong Kong ID cards had also vanished. 'We were looking at some watches and chatting with the people in the shop. I put my bag down and then it was gone,' Mr Gardner said. After the initial shock of losing their valuables, Mr Gardner, a marketing executive, and Ms Kultakham, a student, began to consider their next problem: getting back to Hong Kong without identification. They reported the theft to Shenzhen police, who gave them a report and sent them to a Public Security Bureau (PSB) office - which was closed until Monday. Desperate to get home, they phoned a friend in Hong Kong and he arranged for Hong Kong immigration officials to wait for them if they could get to the Hong Kong side of the border. Mr Gardner, an American, and Ms Kultakham, a Thai national who is resident in Hong Kong, only got as far as the mainland immigration counter. Without passports, they were stuck in Shenzhen, and no amount of pleading was going to change the situation. 'It was like being under arrest,' Mr Gardner said. 'We were trapped in China.' On Monday morning, after checking in with the PSB, they were sent to Guangzhou, the nearest consulate where replacement passports could be obtained. Things went smoothly at the American consulate, but the Thai consulate was closed for that country's queen's birthday. On Tuesday, three days after arriving in Shenzhen, replacement passports in hand, the couple made a second attempt to cross the border, only to be stopped once again, this time because they didn't have a visa allowing them to be on the mainland. It takes about 30 minutes to get a visa to enter Shenzhen, but Mr Gardner said it took three more days to get a visa to leave. On Friday morning, six days after leaving Hong Kong for what was supposed to be an afternoon trip, the weary couple finally made it home. Mr Gardner estimated that his lost property, phone calls, hotel bills and other expenses for the week cost about $20,000. Thankfully, they had plenty of cash and Ms Kultakham's credit card to get through the ordeal. 'It has been a nightmare,' he said. 'I love China and I love the Chinese people, but I don't know if I will ever go back' to the mainland.