Did you take a good look at the bus? There is a good chance it would at least need to be cleaned, even if it was not actually damaged, to prevent a recurrence.
What was on this breaker? Presumably air conditioning running full blast? Might just be a case of "worn out". I have not personally heard of any issues with Crounse Hinds panels, or the Bryant breakers. Let's see if anyone else can comment on that.