BELLEVUE, Wash. – It's been five years since Bellevue Police were called to that road adjacent to I-405; five years since Sky Metalwala disappeared.

Bellevue Police acknowledge they are no closer to solving the case, which started on November 6, 2011.

That's when Julia Biryukova called police to tell them her car ran out of gas, and that she left her 2-year-old son in the car. She said she went out for a walk with her daughter to the nearest gas station, a mile away, and returned to find her son missing.

Police say they determined the car was in working order, and had gas.

"We don't believe he was in the car at the time she said he disappeared,” said Bellevue Assistant Police Chief Pat Arpin.

But they've never made an arrest.

"We still have a detective actively investigating the case," Arpin said Thursday. "We believe at this point, Sky's mother knows more, and we have not been able to get her to come in and talk with us."

BPD claims more than 2,500 tips have come in and thousands of hours have been spent working the case. There is still a full time detective devoted to solving it.

Biryakova has declined all interviews in the years since her son's disappearance, avoiding media and police. Her ex-husband Solomon, has cooperated with Police, and held numerous vigils for his young son. He remains convinced Biryakova knows the full story, and said he has no plans to mark that day his son disappeared.

Court records show Biryakova has since been arrested for theft, remarried, and had another son. Child Protective Services went to court with concerns over the child's safety and Biryakova's "obsessive compulsive disorder.” It's unclear how that case was resolved.

When asked if it was odd for the mother of a missing child to not talk with police, Arpin said yes.

"Is it odd? Yes, it's odd behavior. Why, I can't explain," Arpin said, adding, "She's chosen not to. No interest in helping us any way whatsoever, in helping us with our investigation, so we believe she is the key to solving this."

It's led the Bellevue Police Department and Arpin to also make an unusual request, directly, and publicly to Biryakova.

"Please come help us find your son,” Arpin said.