Hey,
So I kept looking for another answer and found this answer in another thread:
"It is called "sync" for the reason it not called a transfer. It wants and is designed to "sync" make each other match. If it deleted all on the phone it is because you just had zero contacts in the address book on the computer (which on first sync is considered master copy). If you put one dummy contact into address book on computer then try to sync it will see it needs to "merge" to get the sync process coordinated."
I tried it out and it worked. I originally already had one contact in my address book, but it was me and apparently I don't count as a human being, so I added the dummy contact and it worked after I clicked 'Merge'. Hope it works for you too.