iPhone 4 lost contacts only (not recents or sms, etc)

Hello,

So I've recently joined the dataphone community with an iPhone 4. I have been enjoying the phone and learning more about how it works every day, but this weekend, something happened and I'm not sure how, when, or why, and I was wondering if anyone could help me. I only fully realized what happened when my wife called me and it didn't show her name, just her number. Then I checked, and I only had one contact, which I had added the day before. I had noticed that it didn't show any contacts the day before, but I thought I must not have been looking at it right or something, and didn't think anything of it.

Here are the details:

It seems that only my contacts have been cleared, nothing else. My Recent calls, favorites, etc. all retain their numbers, but the contacts database is empty, so there are no names associated with them. The only other thing I saw that was reset were some of my Mail settings (namely default account).

Other than that, nothing seems to have changed. It may have been as early as 3 days ago, to as late as yesterday. Not sure when exactly.

From other threads I've read, it may have to do with syncing, but here I am confused, because I have not done any syncing or updating of the OS or anything. Maybe I updated an app, but I've done that many times without any issues. In fact, I have been intending to learn about syncing, but have not done so yet, thinking that that was only necessary for infrequent, catastrophic problems. I did read something about it automatically syncing with the computer whenever you plug it in to charge? I've done that several times, but never had any issues until now. I also don't use iTunes. In fact, it isn't even installed on our PC, which is what I use most of the time. I have not plugged it into our mac (which does have a version of iTunes on it) recently. It is possible that I plugged it into the computer in the last 3 days, but I don't recall having done so. I've been charging it via the wall jack.

Also, I do not have an "Import from SIM" option in my Settings for "Mail, Contacts, Calendar", which I have heard is supposed to fix the problem. Nor do I have a MobileMe account.

This has totally caught me off-guard, and I'd like any feedback. What could have happened in the absence of a sync or update? Was it automatically updated, and automatically set to delete my contacts without warning? I am using iOS 4.2.6

Thanks for any and all help you can provide in demystifying this for me.

Ray