Hello, being new to this forum, I would like to share with you an unresolved case of disappearance that happened in 2017 in Nantes in France and that we still have absolutely no clue to this day. So I put you in link a subreddit made by a French colleague on reddit which explains everything in English.
In short, Léa Petitgas who lived in Nantes has disappeared without a trace. The only clues the police have is different connections from his phone to neighborhood wifi networks and then nothing.
So I put you, for the most interesting, the link where you will have all the necessary details: