Ear lobe color is determined by genetics. Egg shell color is determined by genetics. There is no genetic link between the two. Most purebred chickens follow the red lobe/brown shell or white lobe/white shell rule, but that's just because the people that designed the breeds did it that way. There are several purebreds that do not follow that rule. Once you start mixing different breeds all rules are off. Red lobe/white shell and white lobe/brown shells are really common. That myth that ear lobe color determines shell color is out there and will never go away, but it is a myth.
There are two basic shell colors, white or blue. Brown or green is just brown laid on top of either white or blue.
@Fuzzy Chicky Mama if you crack one of those brown eggs and look at the shell inside you'll see that it is white. For a hen that lays a brown (or green) egg, the last half hour or so when the egg is still in the shell gland is when that brown is laid on. If, for some reason, the egg is laid a little early it could come out white. The brown had not been applied yet. If that egg shell is kind of thin that would support that theory, it was laid too early.
A hen's internal egg making factory is pretty complicated. Everything has to come together to get a perfect egg. That's not just putting the egg together properly but include when and where to lay it. Often a pullet doesn't necessarily get everything right. That's why it isn't unusual for a pullet to start laying thin-shelled, no-shelled, thick shelled, double yolked, no yolk, or otherwise weird eggs when she first starts. Most of them get the glitches out of their system pretty quickly. To me it's surprising that so many get it right from the start, laying a perfect egg in a nest during daylight hours.
I don't know why that egg is white. It could be a glitch from a pullet just starting to lay, for some reason it was laid a little early (she may heave been disturbed while laying), a defective shell gland, her body did not manufacture the brown coating to put on the egg, she may be a different breed. It's possible that a strange rooster hopped a fence, maybe a few generations back. I consider that unlikely because when you cross a brown egg layer with a white egg layer you should still get a brown egg, just lighter brown. It will be really interesting to see if that white shell color repeats. With it that bright of a white I would expect it to be from a white egg laying hen.
Why would a Buff Orp from McMurray have white ear lobes? That is harder for me to understand. If the person that decides which chickens get to breed uses ear lobe color as a criteria that should not happen. I don't know how McMurray manages that but white ear lobes should have been eliminated from their breeding flock long ago. But even breeders breeding for show get a lot of chicks with flaws.