To qualify for a hardship withdraw the medical need should be a current expense to qualify . If you have outstanding medical bills, that would generally qualify.
Your previous employer does have discretion when making the determination for a hardship withdraw. However, if you feel you are entitled to a hardship withdraw then you should complete your 2017 return accordingly. Understandably, a year from now does not help your situation.
Here is the IRS definition of hardship for a 401(k) plan?
"it must be made on account of an immediate and heavy financial need of the employee and the amount must be necessary to satisfy the financial need. The need of the employee includes the need of the employee's spouse or dependent. "
I am only compensated if you accept the answer. If justanswer charged you, they most certainly didn't compensate me.
However, I will help you anyway I can. It is disappointing that the company didn't approve your hardship given your condition. If you have current medical bills, then I think you have a good argument, but the final decision is at the discretion of your employer, unfortunately.