The terrain in the Victorian Alps has been challenging for investigators.(Nine)
Detectives have established Mr Hill was camping alone with his Landcruiser in the area of King Billy and Bluff Track, between March 11 and 13.
An older person or pair was later sighted at the Black Snake Creek, Eaglevale River crossing and the Ollies Jump area between March 22 and 23, however, police have never been able to determine if it was the missing campers.
Anyone who was in the area of Howitt Plains and Zeka Spur Track on March 19 or 20, the Wonnangatta Valley and Wonnangatta Station between March 20 and 24 who has not yet made contact with police, are urged to come forward.