If the person responsible for your Facebook Business account left abruptly and without giving you the password, you can take several steps to restore access to your company page.
Your first step should be going through the email records you already have. Contact your company's IT specialist, and request access to the work emails of the person responsible for your Facebook Business Account. The password, or a reset link, may be there.
If you still have access to the former admin's work machine, try logging in from there. If they saved the password, you may be able to get into your Facebook Business account quite easily! Reset the password from there.
If that method isn't possible or won't work, try the following.
Every Facebook Business account is linked to a separate Profile. You'll need to access this in order to restore your Facebook Business account.
Go to the Facebook website, and make sure you are logged out. Click Forgotten Account?, under where you enter the password. You'll be prompted for an email address or phone number - ideally this would be the work email for your former coworker, which your IT manager should still have access to.
Enter the email, then access that account for the reset link. You may, in some cases, be prompted by Facebook to verify your business. This is an anti-spam measure, and should be quite easy to comply with.
Once you regain access, immediately make at least two other trusted employees Admins for your Facebook Business Page. This will ensure you don't lose access again, unless something truly catastrophic happens.
If this didn't work and you still don't have access to your Facebook Business account, contact Facebook Customer Service. Be prepared to verify that you are the owner or chief officer of your company. However, be advised that Facebook generally defaults to favor the privacy of individual businesses. They may very well refuse to provide access.
If access to your Facebook Business Page is truly lost, you have little recourse except to create a new Business account. Post several times to the old Page, so your customers are aware of the change. In addition. publicize the change on your other social media platforms. If you don't have any, this is the perfect time to create some! And don't forget the value of Facebook Ads, which can direct your new customers to the new Page.
If you've had to go through this once already, you almost certainly don't want to go through it again. To ensure your company does not lose access to its Facebook Business Page again, observe the following steps: