You can go ahead and create a substitute W-2 so you can file your tax return. You'll need the numbers from your husband's final pay stub for 2017. Please use these instructions: How do I file a substitute W-2 using Form 4852?
If you haven't already notified the IRS about your dilemma, try calling them at 1-800-829-1040. This late in the tax season their phone lines may be very busy, so go ahead and file with the substitute W-2 even if you can't get through to them.