Hopefully someone here can help you but, if not, maybe there is another route to try. I would guess that someone like this would belong to an orchid society or has given talks to orchid societies. If he is in the USA, it might be helpful to go to the websites of the different national conferences and email the poor person who is charitable enough to have agreed to be in charge. Perhaps they could help you. Ours sends emails to our liaison and then an email is sent to all our members if it is of interest. If you know the general area where he lives/lived, that would be even more helpful. Ours covers a wide area including Michigan and New York.
This is the link to my area's conference:
https://midamericanorchids.org/
Another way to find an author is to contact the publisher and they can sometimes help you get in touch with the author.
Good luck!