As you know, the code W amount in box 12 on the W-2 indicates that the employer sent some money either from the employer or from your husband through payroll deduction to an HSA.
I am curious to what HSA they sent the money if your husband's HSA was already closed.
He needs to speak with his HR or benefits people to find out what they actually did. If it turns out that they tried to send the money to an HSA but could not, then your husband deserves a corrected W-2, because as long as that code W is on the W-2, the IRS will assume that he received HSA contributions and will want to see his form 8889.