Came across this Thread just skimming the forums and checking for DUST Beta Keys info. Especially since I know I signed up for Mordu’s Private Trial for what seems like eons ago.
Just do what the OP said in the forum thread post! And apparently quite a few people have just discovered they have a DUST 514 Beta Key they were unaware of.
Log into your EVE Account Management > Services (Drop down Tab) > Voucher Center > ???
If your lucky, you just might find your DUST 514 Beta Key hidden there or maybe not if your unlucky.
Good Luck checking yours! Drop a comment note if you get lucky.