Warner took to Instagram and posted a video, where he revealed that the cap was taken from his backpack while he was commuting to Sydney ahead of Australia's third test with Pakistan at the SCG.

This is my last resort to do this," Warner said.

"A couple of days ago, our bags got freighted via Qantas. We've gone through CCTV footage, they've got some blind spots apparently, we spoke to the Quay West Hotel who we absolutely trust and have gone through their cameras, no one's come into our rooms.

"But unfortunately, someone has taken my backpack out of my actual luggage, which had my backpack and my girls' presents in there, inside this backpack was my baggy green.

"It's sentimental to me, it's something I would love to have back in my hands walking out there come this week. If it is the backpack you really wanted, I have a spare one here, you won't get into trouble.

"Please reach out to Cricket Australia or myself via my social media and I'm happy to give this to you if you return my baggy greens."

The Sydney Test, which starts on Wednesday, marks the 37-year-old's final red ball appearance for his country after more than a decade as Australia's linchpin opener.

At a press conference on Monday, Warner announced he was also retiring from one-day cricket, but would still be available for the T20 format.

He said Australia's upset victory over India in the World Cup final in November was his last 50-over match on the international stage.

He told reporters: "That was something that I had said through the World Cup, get through that, and winning it in India, I think that's a massive achievement.

"So I'll make that decision today, to retire from those forms, which does allow me to go and play some other leagues around the world and sort of get the one-day team moving forward a little bit."