I have had the same problem and still having it to some degree. I sync my BB both at office and home. I only sync the calendar at the office. So to get the appts. off the BB I sync'd it at home device to outlook. then made a .pst of the calendar and loaded that at the office. I had lost the last six months of my calendar, but it was on my BB.
I know make regular .pst backups of my calendar and contacts.
What I have going on now is that I cannot sync all calendar entries or it will crash (my calendar goes back 5 years). So I have it set for 90 days past /future. When I sync it wants to delete entries from outlook for the past items.
Sorry this didn't answer your question, but you are not alone. Also didn't try to hijack.