The protected bird, named Elwood, was the only chick to fledge this year from a nest in Banffshire monitored by the Partnership for Action against Wildlife Crime Scotland.
Data from a transmitter fitted to the youngster showed he left his nest in the hills above the River Spey in early July. He stayed in the area for a couple of weeks before venturing further afield and finally settling in the hills around Tomatin, 20 miles to the south-west, at the end of the month.
The transmitter was providing detailed information about his movements until signals ceased on 3 August.
Elwood’s last recorded position was on a managed moorland a few miles from the Slochd summit on the A9.
Last week it emerged that eight satellite-tagged golden eagles had also gone “off the radar” in the area in the past five years in the Monadhliath mountains – three this spring.
Conservationists at RSPB Scotland, who were analysing transmissions, fear the bird may have been killed to protect game on a shooting estate.
They claim illegal persecution is the most likely explanation and say the case highlights the need for regulation of sporting estates.
“This latest disappearance of a satellite-tagged bird is deeply concerning, and joins the long list of protected birds of prey that have been confirmed to have been illegally killed or disappeared suddenly in this area, said Ian Thomson, the charity’s head of investigations.
“The absence of typical breeding raptor species from areas of suitable habitat or at traditional nesting sites in large parts of the Monadhliaths is further supporting evidence of a major problem with wildlife crime in this general area.”
But land managers insist it is too early to apportion blame for the latest disappearance.
A spokesman for the Scottish Gamekeepers Association (SGA) said: “Getting the facts will be the first step. Speculation at this stage will not help.
“The SGA does not, and will never, condone wildlife crime.”
The most recent national survey, in 2010, revealed there were 505 breeding pairs of hen harriers in Scotland – a decline of 20 per cent since 2004.