You must enter a 1099R for this. The 1099R will show that tax was withheld. The tax withheld is just like when you have tax withheld from a paycheck by an employer. It has to be entered into the return and then the amount of income you received is reconciled with the tax that was withheld to determine if you get a refund or owe more.
Double up on your efforts to contact the retirement plan the money came from.