Bob Pringle says in his annual report that almost 2,900 children and youth were wards of the province in 2012 — continuing a steady decline from about 3,600 in 2008.
But Pringle says about one-third of the children simply grew up and were no longer part of the system.
"The question is ... where have they gone? Have they landed on their feet? Have they got an education? Are they living in poverty? Are they on assistance?" Pringle asked Thursday.
"That group of young people going out of care might not be a good news story. It might be, but it might not be. Chances are that a number of those young people are not doing very well."
Pringle said the number of children in care is also down because more young people are being placed with extended family members instead of in foster homes. It's known as "placement with a person of sufficient interest" or PSI.
That's good in theory, he said, but he added he's concerned that Social Services is not monitoring the kids or the homes.
"That child then does not become a ward, is not in care, and the ministry loses track of those children and young people because they're not in care."
The report highlights one case involving two sisters in Regina. It says the little girls were horribly neglected and abused in a ministry-approved and court-ordered placement with extended family. One of the little girls died.
Social Services Minister June Draude says the ministry is reviewing the standards for such placements with the children's advocate.
"That's something that we are really firmly intent on seeing what we're doing. Are we really protecting the child enough?" she said.
"In the meantime, after that case, we contacted every family that had a PSI child that was under the age of five to ensure they were safe. We made personal contacts with them and that's the type of thing that we will do until we get the report back to ... ensure that all the children that we place are in safe homes, as much as possible."
While the number of children in care is down, the advocate says the number of youth in custody and supervision is up.
Pringle's report says Saskatchewan had an incarceration rate of 23 per 10,000 young people in 2012 — three times the national average and second only to Manitoba.
There were just over 190 young people sentenced to custody in 2012 — up nine from 2011.
"Saskatchewan has on any given day ... more young people ... locked up in closed custody than Alberta and B.C. ... That isn't good enough," he said.
"Even though the numbers have not gone up significantly in the last year, in all categories they've gone up, which is not a good sign."
Corrections officials say the number of young people in custody is actually down from a five-year high in 2008 when 231 youths were in custody.
"Our young people in our facilities has dropped since 2008 and from that standpoint, seeing a drop in our numbers, we're very pleased, albeit we still have more work to do," said Corrections Minister Christine Tell.