Can a personal meeting with a scientist be referenced?
Strictly speaking, yes. The APA style, among others, does have instructions on how to cite private conversations (see https://owl.english.purdue.edu/owl/resource/560/11/ for an example), but in practice I've never seen it been used in psychology (or natural science) papers. This is probably because a personal conversation cannot be easily verified, which makes such citations less useful. One thing you can do is to track down the relevant papers and thank your colleague in the acknowledgement section.