'Upon removing the inspection panel my folks discovered that one of the
two built in breakers is not even hooked up. '

Had one exactly like this 2 weeks ago. It was a 14 kw and only 10 kw was
being energized because the one breaker in Furnace wasnt hooked up.

'Mom says there is one, 60 amp breaker to the unit so my guess is they
didn't run enough power to it'

I think you are correct. A 14 kw. furnace should pull right around 56
amps at 240 v. with motor running. Thats pretty close to a 60 amp
breaker.