I don't think the guy 2000 miles ago would have known unless he was looking.

I haven't had a U-joint failure on the bus but over the years with Corvettes and rear independent suspension I got to see and replace many defective ones. The first sign is that dry reddish powder. It is usually only at one cup. Our buses call for lubrication every 6000 miles or so. How many coaches only get lubed when the oil is changed, and how many oil change intervals are stretched to 20,000 miles? Grease is cheap.

If the U-joint has a grease fitting (factory originals on the Corvette did not) it is because the grease passage to the bearing cup was blocked that a failure occurs prematurely on joints regularly greased. Our buses have two grease fittings 180 degrees opposed. I give each a shot and make sure I see evidence of grease at each cup. So far, so good.