@NernieBichols What you're saying is true, but it doesn't make it right. Ghosting your boss is never ok. If you're old enough to get a job, you're old enough to be responsible and answer the phone. If you can't then go home to mom and dad's because you ain't ready for the real world (which is exactly what he did).
Kids are maturing later in 1st world countries for whatever reason (*ahem* coddling *ahem*). Doesn't make this behavior more acceptable because it can be traced to a cause. Eventually individuals represent themselves no matter how they were raised.
I agree though, 21 is still very young to come to terms with your personal deficiencies, but it is still a very bad look for him professionally no matter the age.