I've fed tons of rat pups to adults. It just takes more pups to feed them, or more often feeds. My snakes haven't ever had an issue constricting rat pups or weanlings or mice.
And as far as "that's all he could get so he shouldn't have gotten a BP" idea... maybe he's been feeding regular sized rats and just now there was a shortage in his area. Perhaps to you, it's better to starve the snake than to give it a smaller than usual meal.
You said it had "good girth" so it's not starved. In my area, no less than 4 rat breeders shut down operations because they were losing money because so many pet stores have gone under. So finding appropriate sized rats(or any rats at all) was a trial for a while. When I found smaller rats, I just got more of them.
But then, perhaps you'll flame me now, since I'm obviously not feeding my snakes correctly and don't know what I'm doing either? Perhaps I should give away my collection, because for a short time I had to scramble to find rodents?
Hmmmmm.
