Unless you synced the contacts with Address Book on your MacBook, the deleted contacts are only available as part of the back-up and can't be extracted separately so you will need to do a restore I'm afraid.
For the future, if you are going to connect your wife's iPhone to your MacBook, I would recommend that you create a user account just for her and then sync her contacts with Address Book, keeping them separate from yours. Alternatively, or in addition, have her sync her contacts with Outlook or Windows Contacts on her PC.
That way, if she loses the phone or there are ever technical problems, you will have a separate back-up on contact information.
The iphone is designed to be synced regularly to a computer. Failing to do this will likely result in loss at some point.
She may be able to restore from the last backup made.
I hear so many horror stories about this, not to mention it happen to me all the time when I got my iPhone 3G. Someone recommended that I set up a Gmail account and sync it through Exchange(m.google.com). Thats all i use now. Whenever I add a contact it is sync'd with my Gmail account and if I restore the phone or whatever all I do is put my gmail info into Exchange and I'm good to go....Just an option..
Similar thing happened to me couple of hours back, I did sync my iphone 4 after 3 weeks, came to work and found out that all my contacts are gone... Apple technology is getting so frustrated day by day... on 1st Jan, I almost missed my work because alarm didnt go... now contacts are gone...
I dont know whats NEXT surprise from apple? They are not doing testings correctly or Its GREED... either way, We are suffering...
I made upgrade of IPhone 3G from 3.0 to 4.2.1 version with ITunes (Win7). After upgrade I get an error information about restore and tried to restore manually. It was completed without problems. After upgrade I noticed there were no contacts. I imported from SIM directly on phone. Today my wife was complaining about missing a lot of contacts.
I have some files in folder C:\Users\MyName\AppData\Roaming\Apple Computer\MobileSync\Backup\657ca985f92136ad040b035506f7633aefbb3831 dated on 27.08.2011, 18:10, just in a time when I continue with restore. Beside, there are some backup files from 28.08.2011 after today's synchro.
I tried to restore data from yesterday backup but it sounds as not valid. Can't see as one backup file in ITunes restore or IPhoneBackupExtractor.
I'll appreciate if someone can help me.