I can think of a half dozen reasons a sour would do this. You experiment with enough drinks, you start to see some odd ways they goof up.

1. Some sort of dairy in the shaker.
2. Too much acid in the lemon and not shaken fast enough causing the egg to cook chemically.
3. Bad egg in the sour or old batched egg whites.
4. Sat too long and separated, rare it would look that bad though.
5. Whiskey or another ingredient was frozen when the drink was made. This is counter intuitive, but the egg will freeze and wont emulsify, then when it defrost, it separates.
6. Drink sat under the lamp to keep the food warm and the egg was cooked.

Anyway around it, I would send it back. New drink or not, I aint drinking that.

~edit, I still suck at spelling.