Digital Editions won't find an accented word wether it searches forward or backward. But, it will find an instance of the word "Lumiere" (without the accent) in the bibliography because it is spelled that way there if you search for it without the accent.
It won't find "Arrivée" on the next line either.
This is a major problem, honestly. In most applications, a non-accented search term will find an accented instance and vice versa. In the very case of Adobe Digital Editions, there is no way to know if an accented word is in a book unless you read up to it. Searching for an accented word with the exact same accented word doesn't find it. A non-accented search term won't find it either.