The regulations provide for some safe harbors:

https://www.law.cornell.edu/cfr/text/26/1.121-3

Does this one apply to you?: "The cessation of employment as a result of which the qualified individual is eligible for unemployment compensation"

Generally you would just file an amended return excluding the gain.  I don't know that "pleading" with the IRS will do much otherwise (although you may find a sympathetic ear to help you work through the 1040X).