Dunkirk is my specialist area. If anyone wants to know anything about Dunkirk just ask. I have over 400 books on the subject and close to 1,000 unit war diaries covering the BEFs time in France between Sept 39 and June 1940.
Going back to the original poster. Do you know the unit he was with and what Port he docked at? I may be able to narrow it down with this info. Sadly, I suspect due to the chaotic times, there are no nominal rolls that I know of that list men to evacuation craft.
Cheers
Andy