Lost all contacts entries: iPhone 4 sync

[Mr. Funtoosh]

With the help of a AT&T staff, I had downloaded all my telephone numbers from my Sprint phone and had synced my whole address book with iPhone 4. Two days ago I was updating my iTunes music by connecting iPhone to my laptop.
Next day I realized that the syncing had deleted all my entries in the Address book and had 'back' synced my old Sprint tel numbers on my iPhone into my laptop Address Book! Now my Phone as well as my laptop have only telephone numbers from my Sprint phone.
Is there any way I can recover my original Address Book (all entries)? I desperately need help as I have lost nearly 300 detail entries. Also, please tell me how I can stop this happening again; I would like to keep old mobile downloaded tel numbers + entries from my laptop address book.

 

[Giaguara]

Did you take a backup with Address Book before you made the first failed sync?
If so you could revert to that backup and add manually the needed numbers or try a new sync.

Once, a long time ago (in Mac OS X 10.2 or was it in 10.3.. anyway, that long ago) Address Book ate each and every contact from my phone and computer that had a US phone number with it. A few hundred contacts completely gone... what saved me at that time was that .Mac had a not synced version, a bit older but still having 95 % of what I needed, so I could use that to rebuild it.

Ever since, each time I do a sync (and even when I don't, once a month doesn't hurt) I do a backup before I sync.
(in Address Book, File > Export > Address Book Archive)