Luke Fergusson's mum urges people to keep looking for him

Sue Bedey said her 28-year-old son, who has autism and disappeared from their Stalworth home on June 9, could be in a shed or structure on someone's block.

"I'm happy to chase any lead, anywhere, because that's what we need. We just need someone to see him so that we've got a point where we can start searching again," Ms Bedey said.

"The locals have turned up on quads and ATVs and motorbikes and horses and we're continuing to do that, even after the police have scaled back the search because we can't stop looking."

Ms Bedey said the police search was 27sq km, but he's more than likely outside of that range.

"Someone may have picked him up and gone, 'oh, this person's not really normal' [and] let [him] out of their car again and so we may be looking in the wrong place," she said.

So far there have been two possible sightings.

A man walking along the road in Murgon matched Mr Fergusson's description, except for the hair.

Then a woman on a property about 6km from them thought she saw him in her paddock.

"He was apparently poking holes in the ground with a stick - that's a pretty typical stress behaviour for someone with autism. We do believe that sighting is Luke," Ms Bedey said.

Police scaled back the search on Sunday following ten days of extensive efforts covering hundreds of square kilometres.

Ms Bedey said their departure left the family feeling lost.

"From the Friday night that Luke was missing, we had police presence on our property the whole time, but on Sunday afternoon, everything was taken away, so we kind of felt very abandoned and lost," she said.

"[It was] not the police intention at all. It was just simply because before, we had activity to keep us busy and you do a lot of thinking when there's not much going on here."

Mr Fergusson's three siblings are taking his disappearance just as hard as mum.

"The youngest (25) feels it the most because she's taking some of the load from me and of course, because I'm not sleeping," Ms Bedey said.

"The only time you don't think about it is that couple of microseconds before you wake up and you think that perhaps everything that's gone on isn't real.

"All the police say is that he's either out of the five kilometre search - which is possible because he's a country kid - or he's deceased, and neither of those sit very comfortably."

It's not the first time the young man has walked a long distance, making the 43km trek from Gatton to Esk when he was a teenager.

However, because the family recently moved to Stalworth from Rockhampton, he may have gotten lost in the new surroundings.

"He's quite capable. His fitness is not in question. His capacity to understand is definitely curtailed," Ms Bedey said.

South Burnett patrol group Inspector Scott Stahlhut said although the investigation into Mr Fergusson's disappearance was continuing, the difficult decision had been made to scale back the search and support had been offered to the family.

"This outcome is heartbreaking for Luke's loved ones and I offer them my condolences on behalf of the service, search party and the community," Mr Stahlhut said.

Mr Stahlhut said an active missing person investigation would remain in place for Mr Fergusson, though search efforts had now concluded.

Beginning Friday June 9, an aerial and land-based search and rescue operation was launched covering a five kilometre radius of a property on Proston Abbeywood Road where Luke left on foot around midday the same day.

The operation also encompassed searches of nearby townships included Proston, Stalworth, Abbeywood and surrounds.

Luke is described as Caucasian, proportionate build, approximately 175cm tall, with brown hair and eyes.

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