A brief trip to Canada and a small paperwork mistake landed a Washington state mother and her 6-year-old son in US immigration detention for more than three weeks, her attorney told CNN.

But Shaw didn’t realize the travel permit that allowed her to exit and re-enter the US had expired. That’s when Shaw and her son, whose immigration documents were valid, were taken into custody by CBP.

Shaw tried to get a humanitarian parole, which would have allowed her to enter the US and return home, but she was denied, her attorney said.

Shaw then asked if her boyfriend or a friend could pick up her son since his documents were up to date, but she was again denied, Thorward said.

They were transported to the South Texas Family Residential Center in Dilley, Texas, roughly 2,000 miles from their home.