It wasn't, sorry. There are farms in the US that try to mimic the process, and there've been cattle flown in from Japan, which might have been what you had (but who knows, the real product isn't trademarked here).
Kobe beef is also around $300-400 for 1kg, so maybe $50-100 in ingredients alone, in Japan, for a burger, let alone what it costs when imported.
Not that it matters a great deal. You probably still got something good. There's other highly (and higher) valued beef in Japan too, Kobe is just a big prestigious brand.
Apparently, "Kobe" is used to describe many things, and, given that a prominent place like the burger bar is still selling their burgers 10 years later, their doesn't appear to be a lot of trademark police chasing people down.
"Kobe beef" is trademarked in Japan and is legally protected there, but not in the US, where anyone is free to use it as they like. You can still prove a beef cut has come from the real source via certification.
These things usually get codified in trade agreements. It seems that Japan hasn't been particularly concerned about protecting Kobe beef internationally, likely because there are so few exports simply due to production limits.
Kobe beef is also around $300-400 for 1kg, so maybe $50-100 in ingredients alone, in Japan, for a burger, let alone what it costs when imported.
Not that it matters a great deal. You probably still got something good. There's other highly (and higher) valued beef in Japan too, Kobe is just a big prestigious brand.