There is a register, however the car must be deemed a total loss.
If a vehicle is flooded and repaired there is no such register, much the same as hail damaged cars, some are repaired (i.e. re-skinned or bodge bogged up) but only those that are total lossed and sent to public auction / tender are registered as being total losses.
There are 2 types of total loss registries............
#1 Structual total loss - These cars even if repaired will never be re-registered.
#2 Economic total loss - No major structual damage however due to being stripped for parts, or multiple air bags going off the cost of the repairs are beyond 70% of the vehicles market value.
Then there is the grey area, a car thats lost its ID plates that is not an economic total loss, nor an economic total loss but has to have a (in Victoria) Police ID number stamped on it in order to have it re-registered usually meaning a major decrease in market value.
Interesting thing however is that there is still not a national Total Loss register, therefore buy a structual total loss in Vic, take it to NSW, garage it for a few months, have it repaired and then re-register it in NSW, as far as I am aware, the NSW RTA still dont check with Victorian VicRoads as to its history.
Or, buy one at auction, then store it for 7 years after which all it's history is binned from VicRoads data base, no more total loss history.
Cheers
John