If you really wanted to, you probably could track the guy down. Still have any old yearbooks? If not, the school probably keeps archival copies. You could go through old yearbooks of the appropriate age until you find the guy, then try to find him on Facebook or other social media. And asking through networks of friends and acquaintances could help in a similar way. Whether you want to or not is another matter, but 20 years ago isn’t that long. It should be entirely possible to track this person down if you wanted to badly enough.