Understanding Thermal Characteristics for Microchip CL2N3-G Constant Current LED Driver
Actually, I think you are correct. That chip is designed to drive lots of LEDs in series, which is why such a high voltage is needed. If there's only one LED then the poor chip has to drop 58V, which as you say is over a watt of dissipation which is too much for that package.
If you truly just want to light one LED @20mA and the only rail you have is 60V, then any linear circuit is going to have to dissipate that 1.2W (60V * .02A) somewhere.
The only way around it is to add a switching regulator to generate a more suitable voltage, say 5V, and drive the LED from that. Unlike a linear regulator, with a switcher the power in more or less equals the power out, so you'll only draw about 20mA * 5V/60V = 1.7mA from the 60V rail (0.1W).