Yes I agree with CP and I say this as a Black woman. And I hate to be too cynical BUT some people complain and speak to mgmt to get a free meal. Who knows if that's the case here. The complaint just seemed so disproportionate to the minor mistake that was made. IMO it was either a strategic move on their part (or they just seized an opportunity) or hypersensitivity to racism.
A good mgr will recognize you did nothing racist and won't ever even mention it again. Sounds like that's what your mgr did so chalk this one up to experience and don't give it a further thought.