[RegW]

On reflection, I think a more likely explanation is that Facebook just harvested, used and shared your WhatsApp metadata. Metadata analysis doesn't seem to count as an invasion of privacy in the modern world.

So while you and your friend chatted about this college, perhaps your friend googled it.

FB might then share with Google that you connected with your fiend at that particular time, and Google connected your exchange with the search.

Of course this assumes there is some way to tie your FB and Google accounts together - like matching up shared FB & Google tracker journeys across the internet.