I received a w2 from a previous employee. I did not work for the company in 2018 but I was refunded money that was owed to me

"REFUNDED" money? Did you loan money to the employer and they paid you back? I doubt it. Sounds to me like you were paid wages that you were owed. If so, if the wages were paid to you in 2018, then the employer would be required to issue you a 2018 form W-2 to report those wages paid to you. It doesn't matter if you actually earned those wages 10 years ago. Your wages are reported as taxable income in the tax year you are paid that money, and it doesn't matter in what tax year you may have worked and earned it.

But to be sure here, it is a TWENTY EIGHTEEN W-2 you received, right? If not, then what tax year is printed on the W-2?