This case is absolutely not documented. It is pure hazard which brought it to my attention.
A while ago, a person I know visited my family to present his best wishes for the new year. He saw on the monitor of one of my computers a page from this site devoted to UFOS. I do not in general mention my interest for this question, as very few people are interested in it, almost nobody takes the subject seriously, and a short informal discussion of the topic will not help anyone to form an opinion on the matter. So this person had no idea that I had any interest in ufology.
Here is the transcription of what this person told me then. I know him enough, he is not a practical joker of any kind:
Ufos? oh yes ufos ... Actually there was something when I was (young? a kid?) at Merxheim (smalltown where the person spent his youth).
Somebody saw an UFO landing in a field. A kind of "arm" came out of it and grasped some cabbage in the field. (At this step we all made funny comments because a well known French comedy of the sixties is about aliens coming to earth to taste cabbage soup)
Some kids saw it also when it fled. It made quite an impression in the village. Jean-Claude Bourret (*) came, also.
So there was a rather spectacular case of ufo landing, if this account is correct, with arrival of a journalist known for its (financial) interest in the UFOS, probably coming from Paris. I wondered if there was any mention of the case in the media but at this time I found none.
But it is actually after this conversation that I decided to search if there were ufo cases in my region, Alsace, and what kind of media impact they might have received.
Jean Claude Bourret's career is totally burned out now, both as TV presenter and author of ufo books. No French media top personality will ever even mention a belief in ufo reality now.