Friends of mine recently lost their website because the domain name expired. They claimed it was stolen. I would claim they didn't take the responsibility required to be in business today.
- Know who your domain name/s is/are registered with.
- Make sure auto-renew is enabled.
- Make sure the credit card details are updated.
- Know who your web hosting is with, and do the same.
- Know who your email is with, and do the same.
Finally, check your spam folder on the regular. Often sitting alongside diet pill emails and someone selling SEO services is an important email that my mail provider has marked as spam.
If you leave your wallet open on the street out the front of your house it may well be stolen, but you dropped the ball by leaving it there in the first place.