[George]

Sorry to hear your loss.
Golden angelfish is one of the most shy fish, angelfish or otherwise, that I have ever owned. It has to be very comfortable with its environment before it even starts eating. I have one close to 2 years now. It only comes out during feeding time and hides most of time.
A good quarantine protocol is probably the best to keep this fish. Not only to make sure it's disease free, most importantly to make sure it is eating and fat before being added to DT.