The woman vanished. Nearly 2 years later, family, friends, detectives seek answers. Where is Heidi Planck?

Nearly two years since Heidi Planck disappeared, her friends and family, including her 13-year-old son, have no answers as to what happened to the 39-year-old mother.

Surveillance video shows her going into a downtown L.A. apartment building, but there’s no video showing her leaving. A search for her body in a Castaic landfill yielded no answers.

“We are kind of nowhere because they haven’t found anything,” said Jim Wayne, Planck’s ex-husband. “I’m just hopeful that if somebody saw something, they would come forward and say, ‘I know who did it.’ ”

Now, in an effort to encourage possible witnesses to come forward, as well as to try to keep Planck’s case in the public eye, her friends have posted her picture on billboards across Los Angeles.

“Maybe they’ll trigger somebody’s guilty conscience,” said Danielle Nadolny, a friend of Planck’s. “Maybe she’s dead, but where is the body? Or who had the ability to hide her body so well that the most elite detectives in Los Angeles can’t find her?”

“MISSING MOM,” the billboards read in large red letters, along with pictures of Planck.

The messages are set to remain on the billboards through the month of October, drawing the attention of drivers and pedestrians along busy streets near the intersections of Venice Boulevard and Olive Street, Olympic Boulevard and Hill Street, and 12th Street and South Broadway, and on the westbound side of the 10 Freeway near San Pedro Street.

“At the end of the day, when a mother gets thrown out like trash and discarded like that, it pisses a lot of people off,” said a friend of Planck’s who helped arrange for the advertisements but asked not to be identified to protect her privacy.

Planck was reported missing by Wayne, who called police three days after she failed to pick up their son from school.

Planck was last seen Oct. 17, 2021, when, according to Wayne, she left in the middle of their son’s football game after looking “a little antsy.”

“I just remember her saying, ‘I’ve got to leave,’” he said at the time.

Police would later find that Planck at one point made her way to a luxury apartment in downtown L.A., where she did not live, on South Hope Street.

Planck’s dog was found inside the apartment building. Police said forensic evidence found inside the building “led detectives to believe an incident occurred resulting in Planck’s death.”

But what happened to Planck inside the building — and why surveillance video of the building showed her going into the building but not out — is unknown.

In November, the investigation into Planck’s disappearance led investigators to a landfill in Castaic. Heavy machinery could be seen digging through the area but to no avail.

This week, LAPD officials said Planck’s case, which is being handled by the department’s robbery-homicide division, is still open and actively being worked.

Wayne said October is a difficult time for him and their son, who are still grappling with the lack of answers. Sometimes, the two stay up at night, remember Planck and try to encourage each other that there will be answers, at some point.

“This is not an easy endeavor,” Wayne said. “It’s a rough time of year for the little guy because it just brings all this stuff up.”

Still, he said he’s encouraged that the LAPD has continued chasing leads in the case.

Planck’s friend who helped arrange the billboards said she hoped the advertisements would serve as a reminder to anyone involved in Planck’s disappearance that, even as time goes by, the pressure to find answers won’t stop.

“It’s not going away,” she said. “It’s been two years, and it’s only going to get louder and louder.”