So the delight to have found these:
The chance to find out never came, though. They are completely, entirely gone. They are the second pair do disappear; a pair of pink high heels from 2013 also went missing, in 2014, and never showed up since. Lost in my flat! The brown pair vanished somewhere between Calasparra and Murcia, i.e. I have no good explanation. I searched and searched. Have you also lost something you should not have lost? I can make my list longer; there is a white blouse, a booklet and a jacket that seem to be eradicated from earth's surface.