I have never seen anything related to my DITY moves show up in MyPay, i.e. the moneypot for however you move your HHG is completely seperate from your travel money (which DOES show up in MyPay) for any given move. I've done 2.5 moves in the last 3 years (2 PCS partial-DITY and one TDY full-DITY). Every DITY has had it's own W-2 show up in the mail at the ass-end of the legal delivery window in which employers are alloted to provide a W-2, not with the check. DITY payouts will get a W-2 (not a 1099) because they are considered Incentive PAY. I have never had to go out of my way to request a W-2. Beyond that, my only advice is to keep track of how many DITYs (tdy or pcs) you've done in a calender year (to know how many to expect), otherwise you may find yourself having to amend your tax return as I have.
Unfortunately, I can't answer the original concern.. I have no idea who to talk to to get a duplicate W-2 sent out. I can say they are in Norfolk though, as I have actually talked to them... once.