How would one know if their phone was or is afflicted by the recent bug (sending sms to the wrong people)?
From this post, it seems that only very specific conditions seem to trigger this bug. Also, AFAIK, this only seems to affect the default Messaging app, using a replacement like Handcent seems to be the way to go. More info on the bug here.
Specifically, there is something about certain email-to-SMS messages that corrupts Android's SQLite database, causing unpredictable results thereafter. The most commonly cited offender is alerts sent by Bank of America, though SMS alerts sent by LinkedIn and T-Mobile are also cited. It's possible that any SMS where the sender is an email address will do the trick, or it's possible there's something else these specific senders' messages have in common.
To be clear: if you've never received one of these corrupting messages, you will never be able to reproduce the bug. That's why it's only affecting a small group of Android users.
If you have fallen prey to the issue, you should be able to fix it by performing a hard reset (wiping all data) and then blocking the offending sender(s) from sending you texts in the future.