It's not mislocated note :) There is something, look at Google Street View: https://www.google.pl/maps/@46.9379777,5.8773035,3a,23.2y,249.16h,79.44t/data=!3m6!1e1!3m4!1sIyFEz89KimLVLAe3vTLD2w!2e0!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI0MDkxMC4wIKXMDSoASAFQAw%3D%3D
and look here:
https://www.wimvansijl.eu/ORDE_DER_RIETJES/05_l_ORDRE_DES_PAILLES.html

There is quite similar object in my town, Janów Lubelski, Poland (look at https://www.wimvansijl.eu/ORDE_DER_RIETJES/04_FUNDACJA_ZAKONU_SLOMEK_2.html 
and Google street view: https://www.google.pl/maps/@50.7049439,22.4181365,3a,15.2y,299.24h,80.15t/data=!3m6!1e1!3m4!1snlrYroTqM2KZM_ncHejZSw!2e0!7i16384!8i8192?entry=ttu&g_ep=EgoyMDI0MDkxMC4wIKXMDSoASAFQAw%3D%3D) 
Both objects have very similar or the same plaques (https://www.wimvansijl.eu/ORDE_DER_RIETJES/00_ORDE_DER_RIETJES.html)

I have no idea what is it. Maybe it's kind of joke? Or some kind of artistic performance by Dutchman Wim Van Sijl? 
Object in my town is quite new, constructed specifically for this strange plaque. I guess object in France is maybe part of ventilation system of salt mine and maybe somebody added a plaque? 