It's a shame showing a lack of successful measurement isn't rewarded or even encouraged.

Truth. I got scooped once, by a matter of days, was just about to submit to a journal, and one of my advisors said, basically, "oh well. next time." I was like "well it's kind of a complimentary paper, reconfirming the same physics", and they said "so what? you gotta be first." Same idea, though. Even though the paper would have contributed to the field, I was discouraged from publication. I should've published anyway, in hindsight, just like all the null results and other reconfirmations. But especially so, because the paper was already written and everything.

grad students span gamut from 'wait, why isn't B a constant?' out-of-their-depth beginners to the likes of you, who probably shake their head at visiting professors' inexperience with methodology.

Eh, not common at all. Only once has this very notably happened, I think, when some theorists with no idea how particle spectrometers work were trying to use our data to do something with relativistic gauge invariance. They got shot down pretty badly at a conference. I just went off googling, and I can see they never published. Righteous, the process works! But it's very true that grad students in physics are selected primarily through their skills in mathematics, which is obviously necessary, but I've seen how often some of the students very skilled with maths struggle when they get into research. Creativity, critical thinking, and math skillz rolled into a single person is super rare. There were only one or two people in my class of twenty that had all three, and it sure as hell wasn't me.

By the way, it's funny because I'm still in grad school, hah, for just one more week! Fell off the wagon for a few years. Went to rehab for booze. Doing much better. I should probably write a pretty lengthy post about rehab, though. My god, what a funny experience.