Jessica Herringa made her last sale at the Exxon station at 11 p.m. Saturday, ABC News reported Sunday.
A witness saw her "walk out of the store with this guy like there was no problem" but a struggle ensued when they got to the van, her mother, Shelly Herringa, said.
Jessica Herringa had been preparing to close up the store -- she had her nightly cleaning supplies out -- and would have left for home about 15 minutes later, her mother said.
Police were alerted to the woman's disappearance by a customer who called to say there were no employees when he stopped at the gas station, ABC News said.
North Shores Police Chief Daniel Shaw said robbery did not appear to be the motive for the abduction because the store's cash register was left untouched.
There were no surveillance cameras at the station but police said they were looking for a silver minivan, possibly a Chrysler Town and Country, seen in the area before the woman's disappearance.
"If somebody did take her, I wish they would just drop her some place so she could come home," Shelly Herringa said. "She's just a hard-working girl. She was trying to support her child."