After it’s capture, the burnous was given to the Prussian general Marshal Blücher, who in turn, presented it to the Prince of Wales, the Prince Regent. It is now in the Royal Collection at Windsor Castle.
It function and style, it definitely seems more of a garment to be worn by his Mameluke attired servant. However, the quality and materials makes it more likely to be his though. I wonder though if in Europe it was more of a housecoat or dressing gown, to be cast over Napoleon’s nightclothes when moving around a draughty palace or grounds?
Unless there is some written or pictorial evidence that Napoleon wore such a cloak between 1799 and 1815, it is highly unlikely that this was an item of clothing owned by the Emperor. It might have been captured by the Prussians in 1815 as stated, but the attribution of ownership to Napoleon is unproven (and probably unproveable).
Do we know more about this other than the NAF
At Marengo he already wore the legendary grey great coat - and how did the Prussians capture this specimen?