The motorcyclist dropped a bag with jewels and hatchets when his motorcycle hit a pedestrian during his escape.
"The loss is very high and remains to be assessed", one police source said.
Three axe-wielding thieves carried out the brazen robbery late on Wednesday at the ultra-chic hotel on the city centre's Place Vendome, next to the Justice Ministry.
All of the jewels looted in a multi-million-euro robbery at the Ritz hotel in Paris have been recovered, a source close to the case said Thursday, as a police hunt for two of the robbers continued.
Authorities did not say where in the hotel the bag was found, nor did they say how it may have been separated from the robbers.
Another police official said some of the thieves apparently had guns.
The accomplices outside fled, one on a motorcycle and another in a vehicle - which French media reported was found burnt out in Val-d'Oise, about 30 kilometres north of Paris.
The luxurious five-star hotel is located in Place Vendôme, in Paris's historical first district on the right bank of the river Seine.
Hemingway famously "liberated" the bar after arriving in Parison a tank at the end of the German Occupation in 1944.
The hotel was bought in 1979 by Egyptian billionaire Mohamed Al-Fayed, whose son Dodi was also killed in the fatal crash.
It was the last place Princess Diana stayed before her fatal vehicle crash in a Paris tunnel, and hosts elite guests from around the world who prize the refined neighbourhood.
A superior room at the hotel costs from £885 a night, while a "grand deluxe" room could set guests back £1,240.
The heist took place about 6:30 p.m.
Over the last few years police have kept a permanent presence in the area, but they have not deterred potential robbers.
Three men were arrested as they tried to flee by the way they came in with bags of gems and watches worth over 4 million euros ($4.8 million) but came up against locked doors.
Kim Kardashian West said she lost millions of dollars worth of jewellery when she was robbed at gunpoint in a Paris apartment in October 2016.