A little bit over 20 years ago but on Feb 1 1993 a Nord Mohawk 298 VH-HKS lost a prop somewhere over the national park area just north of Sydney whilst en-route to Tamworth. Don't think it was ever found.
Here are two earlier prop and engine loss events
1964 Ansett ANA DC6B VH INA lost prop from RH inner due fatigue fracture after take off Essendon then engine itself fell off. Landed safe
1940 ANA C2 VH USY right hand engine fell off after engine fire. Landed safe NHill.