I don't know about the RL gold paint, but it probably has a lot of pigment. Paints with a lot of pigment (deep tint base) require a minimum of two coats. RL paints also require take extra time. Many pros I know avoid RL paints because of the work involved - most h/o don't believe the extra cost and blame the painter. The painter only did one coat? Painter should have known better. Painter needs to come back and put on a second coat.
If you and painter only agreed to one coat, pay him for the second coat.