Your dad sounds awesome.

If your dad loves the work, okay cool. But your effective implication is you cannot have anyone else do this, which is obviously absurd because there are companies much much larger than either of ours that pull it off.

The key point is not "the owner has to do it", it's someone has to be held responsible for this.

For smaller businesses, it's likely the owner. For someone like your dad's, it's usually someone else. Even a solid bookkeeping system would have picked up what OP missed.

> you develop a sixth sense for problems

100% agreed, but for the owner/operator it's usually all things, but for the person who is responsible, it's usually a lot more of the minutiae.

It's literally impossible to be the master of all things.