Yacoma In that case it could be possible the two "talked" to each other and exchanged data via IPC in the same profile and via the loopback interface communication hack (still unpatched AFAIK) if in different profile (my guess).
However if the original install of the non-business whatsapp had no perms and still managed to get your phone num, that would be interesting - not sure how it could unless there's a colluding app which had the required perms and the apps, well, colluded.