You can not recover history that has been deleted.

It sounds like the Facebook password has been deleted. You should be able to reset your Facebook password - https://www.facebook.com/recover.php

My Facebook password is still valid. Because I deleted the history, it also deleted the information regarding my computer so Facebook is not recognizing my computer.

Facebook does not need any of the history in Firefox. Deleting history does not delete data about the computer.

What is the full error message that you are getting?

Facebook has a new security option that allows users to register their cell phone number. If an unknown device tries to access my Facebook account, Facebook will send a code via text message. This code must be used in order to access Facebook. My cell phone number was deleted from Facebook and I deleted the history. Once I deleted the history, my computer is no longer recognized by Facebook. When I log into Facebook, I receive an error that states that I don't have a phone number listed on my account. Please login from a recognized device to regain access to your account.

I delete my history frequently. One I do this and log into Facebook, a code is sent to me via text so that I can log in from an unknown device. Since there's no phone number listed on my account and I deleted my history, I cannot log into Facebook.

I was trying to restore my history thru index.dat file.

index.dat is not one of the files used by Firefox, that is for Internet Explorer. You may need to contact Facebook to get access to your account again.

Once history and cookies are deleted in Firefox they can not be recovered.

I was afraid of that. Thank you.

hay katie028 .. i am also facing the same issue. Please tell whether you got back your account or not. Please Do tell me .. I don't know how my cell no is deleted. :(

Most likely it was cookies as well as history that were deleted. You should be able to log into Facebook again to access your account.

I am having the same issue- Im locked out of my own account and no devices are recognized. Im so bummed! Of all the times- im at my best friends wedding. Has anyone been able to resolve this issue? I havent gotten a response from the facebook team and so far have absolutely no leads on how to fix. I tried password reset and new codes to my cell, but my phone is also not recognized.