A couple of years ago, I was at a conference and there was the typical Q&A after someone gave a talk. I can't even remember what is was about, however in the audience was one of the big-shot researchers in my field (papers, citations, grantmoney). She made a comment, that kept stuck in my mind, and now I would like to borrow that information for my thesis. Can I cite this as a personal communication?
Note, I have not talked personally to her, just was in the audience and "overheard" the comment. Note also, what she said was related to some government research contract, and is not published.
Edit: some clarifications:
It was a public comment on the talk, made to the whole audience.
She mentioned that they are using a certain instrument in their research (the government thing), which I like to mention in order to point out the relevance of that instrument even in other areas than what my own reserach is covering.