By Agence France-Presse
Cedella Roman, 19, ran across the border just south of the town of White Rock in Canada's British Columbia, into the US state of Washington on the evening of May 21, she told the Canadian Broadcasting Corporation (CBC).
She headed back when the tide began to come in, going up toward a dirt path before stopping to take a photo of the stunning scenery, then turned around to retrace her steps.
It was then that she was apprehended by two US Border Patrol officers who told her she had crossed illegally and had been caught on camera.
"I told him I had not done it on purpose, and that I didn't understand what was happening," she told CBC.
Roman protested that she hadn't seen any warning signs, and didn't initially anticipate how serious the matter would become.
"I said to myself, well I may have crossed the border -- but they'll probably only give me a fine or they'll tell me to go back to Canada or they'll give me a warning."
Complicating matters, Roman, who had come to Canada to visit her mother and work on her English, wasn't carrying any government-issued ID on her at the time.
She was transferred by the officers to the Tacoma Northwest Detention Center, run by the Department of Homeland Security, 200 kilometers (120 miles) to the south.
"They put me in the caged vehicles and brought me into their facility," she said. "They asked me to remove all my personal belongings with my jewelry, they searched me everywhere.
"Then I understood it was getting very serious, and I started to cry a bit."
When she reached the center, she contacted her mother, Christiane Ferne, who quickly reached the center with her passport and study permits -- but the workers at the site said the documents would have to be verified by Canadian authorities.
She was held at the center for two weeks before the matter was resolved and she was allowed to return to Canada.
Ferne said the lack of clear signs had led to her daughter's predicament. "It's like a trap... anybody can be caught at the border like this," she said.
US Immigration and Customs Enforcement confirmed to CBC that Roman was discharged on June 6. But neither the ICE nor Immigration Canada would comment further on the case, citing privacy concerns.
A spokesperson for the US Customs and Border Protection told CBC that anyone who enters the US outside an official port of entry and without inspection has crossed the border illegally and will be detained.
"This applies regardless of whether or not the individual claims to have inadvertently crossed the border," the department said.