Caravan Park owner Guy Royale said the leg was stored in the park's freezer for two days until Esperance police collected it on Friday.

The police refused to disclose what has happened to leg that saying that the family had requested that this information not be made public.

Spokesman Roger Gough said Zac has been told about the discovery and was not concerned about its whereabouts at present and just wanted to concentrate on his recovery.

CSIRO great white shark research scientist Barry Bruce said there are many reasons why the shark might have let the leg go and did not consume it.

"The shark may not have had hold of the leg and dropped it," he said.

"We see the same sort of pattern on seals where they are partly consumed and it is all part of the hunting process."

Mr Bruce believes that it was the quick thinking of Zac's brother who removed Zac from the water that saved him from further attacks by the shark.

"This is the main reason why swimmers and surfers should never swim alone," he said.

Zac is reported to be doing very well and is expected to return to Esperance within the next two weeks after rehabilitation at Shenton Park Hospice.

"He's really a switched on kid and he just wants to come home," Mr Gough said.

On arrival at Esperance Hospital after the attack, Zac requested that he not receive any blood transfusions in accordance to his beliefs as a Jehovah's Witness.

Mr Gough said doctors told him that Zac did not need a blood transfusion anyway because his blood count was so good.