On the website that now displays the part of Grothendieck's archives that had been held at the University of Montpellier, it is mentioned that:
Dans une lettre adressée à Monsieur Lefranc datée du 13 octobre 1985 (voir cote 183/97), Grothendieck évoque la disparition de sa correspondance allant de S à Z. Il affirme que ces documents se sont volatilisés à l’occasion du « sac » de son bureau la même année.
(Own translation: In a letter addressed to Monsieur Lefranc dated October 13, 1985 (see reference 183/97), Grothendieck addresses the disappearance of his correspondence from S to Z. He asserts that these documents vanished on the occasion of the "burglary" of his office that same year.)
I'm interested in facts about this.
Is it true that these letters were stolen?
If so, then who might have been the perpetrators and what might have been their motives? And is it then possible that historically interesting letters, from perhaps Tate or Serre, might have been lost?