If Buchanan's sold you spokes and a rim for a specific hub, 99.9% they got it right. I've never had a problem with their products or on-file specs. I've never measured any of my wheels for them and have paired some oddball stuff together (19" Sun rim to a CB front hub with heavy duty spokes/nipples, Suzuki GT750 front hub to an XS650 rear rim etc.)
And if they did get it wrong, I have no doubt they'll make it right. But take a pic of your wheel - till then nobody can tell you if you've laced it right. Or find your local guru (my guy laces wheels for all the local vintage racers).
Where are you located? I'm in Toronto.