I agree with you up to the last paragraph. It sounds to me like the led is reverse biased like a silicon particle detector. A normal led works by combining electrons and holes to make photons, in this case hole-electron pairs are made by light. The reverse bias causes them to drift apart, resulting in a small current opposing the bias.

For this reason i would interpret the power supply producing the bias as the load, and the led as the power supply. This is how energy is removed from the system.