The hooker, who plays for Cornish Pirates in the English Championship, started for the Fijians in their matches versus Australia, Georgia and Wales and came off the bench in their other pool game versus Uruguay at the finals in Japan.
It capped an incredible year so far for Matavesi, who also featured for Toulouse this year as a short-term medical cover signing towards the end of the Top 14 season.
However, the 27-year-old has now taken to social media in the hope that some treasured possessions collected in Japan can be returned to him.
Matavesi revealed that an overnight stay in Shoreditch in the English capital was ruined by the theft of bags he had left in a car parked overnight at a Finsbury Square car park.
According to his online message for help, the bags contained three Fiji World Cup jerseys, other signed Fijian shirts, his World Cup cap and presentation medal, rugby kit, boots, trainers, gym shoes, other personal belongings and rugby memorabilia.
Matavesi asked followers: “Could you please share this and look out for any shirts/kit/boots etc that come up online, or you hear or see anything from around the area?”
His message has been retweeted on Twitter nearly 900 times, with legendary Fijian Nemani Nadolo among those alerting people to Matavesi’s misfortune.
Matavesi joined Cornish in December 2017 having played for Camborne, Plymouth and Redruth and last November bridged a five-year gap between caps when chosen to start for the first time since 2013 in matches versus Scotland and France.
He had been combined his rugby at Cornish with work as a supply chain logistician at the Royal Naval Air Station Culdrose near Helston.