It's not common by any means, but in certain circumstances, it is possible to seemingly—or actually—delete your homepage. Even though the few seconds after discovering this occurrence might give you a sense of panic and cause you to break out in a cold sweat, a simple solution is available to help you fix the situation.

Causes and Fixes

Cause #1 Menu Change
Your site initially comes with a page designated by the site as your home page, accessible by a menu link in the Main Menu link list that defines what appears in your primary navigation bar on the site. If this link is disabled or deleted it can seem like your home page has been deleted.

Solution:

1. Navigate to Shortcuts » Main Menu.
2. Locate your Home (disabled) link and check the box next to it to re-enable it.
3. Click Save to finish.
4. Check that your homepage has returned.

Cause #2 Page name change
You may have created your own homepage and decided to update or change its URL Path Settings information, which is located on the right side of the Edit screen under Additional Options. Doing this means that the path information is out of sync with the name of the page the site has been configured to target.

Solution:

1. Navigate to Manage » Configuration » System » Basic Site Settings.
2. Locate the section labeled "Front Page".
3. Update the pathway information in the URL field provided to match the new page URL Pathway information you created in your custom home page.
4. Click Save configuration to finish.
5. Check that your homepage has returned.

Cause #3 Custom homepage deleted
If you created your own homepage, linked it in the Basic Site Settings area, and then deleted it by accident this would certainly result in a missing homepage. 

Solution:

1. Create a new Basic Page and provide it with an easily identified Title and/or URL Pathway Settings name.
2. Navigate to Manage » Configuration » System » Basic Site Settings.
3. Locate the section labeled "Front Page".
4. Update the pathway information in the URL field provided to match the new page URL Pathway information you created in your new custom homepage.
5. Click Save configuration to finish.
6. Check that your homepage has returned. Any associated blocks that were instructed to appear on the entire site or specifically '<front>' will show up automatically.