From my own personal experience (broken my wrist twice, but definitely NOT a doctor), it’s not uncommon for some fractures to not show on x-rays until they’ve calcified - usually a couple of weeks later. This happened the first time I broke my wrist. I didn’t even have much swelling, but the doctor treated it conservatively and casted it for a couple of weeks as a precaution. Sure enough, after we took the cast off, he spotted a hairline fracture.
The second time I broke my wrist, it was really obvious and had to have surgery the next day, but that’s a different story.
Without any inside information, and going off of pure speculation, I’d imagine that Caleb fell on his wrist, x-rays came back negative so, being a tough kid, he gritted it out. Now that he’s gone back home and had it re-examined after its continued to hurt, they found a fracture. Considering he doesn’t need surgery and is only in a cast for 4 weeks, I’d imagine it’s pretty minor.
Sucks for him, and I can understand people questioning the staff, but these things do happen.