I'd love to see that photo, it'd be a learning experience. I have questions though, in the picture was a portion of the wheel still being held in place or was it just an empty axle with a nut and cotter pin? And wouldn't that photo been taken at LAX after they landed? I can post a picture of darn near anything and claim it's something completely different.
Based on that picture it looks like the wheel failed, you can see the bolts used to secure the axle nut still installed. I'd like to point out the wheel speed transducer that appears to be completely destroyed also still being installed in the axle by the same two bolts. The inboard roller bearing inner race looks to be in its proper position and I suspect that dangly looking ring is its outer race. The outboard bearing looks like it completely failed and because the rest of the wheel in its entirety is missing it might be the initial part that failed. I've never changed a wheel on an airliner and the largest airplane I've changed wheels on would be a Global 5000 or a G650 but I'd assume the concept is basically the same, just bigger and heavier. Most folks look at jet wheels and assume they're built like the wheels on their cars, they're not, especially the MLG wheels. In the olden times, including some Gulfstreams, when you remove a wheel you would clean, inspect and repack the bearings before you reinstall them, newer airplanes have the bearings as part of the wheel assembly (this saves time and money spent on gloves and grease). In all of my time working on 135 airplanes I've changed hundreds, maybe thousands of wheels, I've changed tires three times, the point is if your following the AMM or CMM and you want to just change a tire you need to tear down the wheel assembly, clean it, inspect it (this may or may not include NDT such as MPI for cross bolts and Eddy Current for the bead area on the rim) and then reassemble this thorn in your side, sign it off and then reinstall it. The reason why I've only changed three tires is because most folks don't want to have a tire shop in house so they use a vendor and all of the wheels went out and came back with an 8130-3, a brand new tire and some evidence of grease on the bearing covers. I don't know if United has a tire shop in house or contracts that shop work out to vendors. Was that outboard bearing cleaned, inspected and packed full of grease before it was installed? I don't know. Here's the other part of it, doing something so routine like changing a wheel can lead to complacency and despite the pitfalls some folks might cut corners. In my experience when you install one of these wheels, again these things weigh a couple hundred pounds and the tolerance between the axle and the bearings (the only actual parts that touch each other between the axle and the wheel other than the nut that retains them) is usually less than .001". So it is rarely anything other than a wrestling match with a 200lb inanimate • to get the brakes and the bearings lined up and get the wheel seated. That's normally when folks will take a second to catch their breath and gather up their torque wrenches. The AMM will give a procedure that the wheel needs to be rotated as the axle nut is torqued to seat the bearings, the initial torque is actually an aggressive overtorque. If you follow the procedure the next step is to loosen the nut and then retorque it as the wheel is being spun. At that point a normal person might think they're almost done, nope. If you look in that picture you can see the castellations in the axle nut, those and a series of holes in the axle need to line up to not only secure the axle nut but also the wheel speed transducer. So a person might wonder how is this apparent obstacle overcome? It's not a game ender if the holes don't line up on the first try, the AMM gives a fairly wide torque range as the final torque and if you've done this once or twice you start at the lowest setting and work up in increments. What if the holes don't line up in the torque range? Start over and try again, you'd be amazed how all of these parts want to work together. Or just remove the axle nut washer and "clean" it with some Scotchbrite or sandpaper, it doesn't take much to get things squared away and everything will line up. Then you can put the hubcap on (that's what spins the transducer) safety those bolts, service the tire (that requires a nitrogen bottle, can you carry one?) lower the airplane back on to the ramp (did I forget to mention airplanes also need jacks? Axle jacks, look it up) and then just walk away.
Gotta check your nuts on the walk around.
