According to CASA website VH-PGA is not on the register
Indeed, no VH-PGA on the CASA register. However there was a C208 VH-PGA at least in 2015 - see ATSB
Investigation number: AO-2015-083:
Near collision involving Cessna 210L, VH-TCI, and Cessna 208, VH-PGA 46 km NNE of Broome Airport, WA on 15 July 2015
Regosearch states:
Here are the Australian aviation rego search results for 'VH-PGA'.
The aircraft registration database was last refreshed from the Australian Civil Aviation Safety Authority (CASA) on 03/Apr/2018
So, VH-PGA appears to have existed on the Register only four days ago?
Intriguing?