Bram, do you have a backup of your wallet.dat at some point in time before you used a password or maybe I misunderstood, are you saying you were hacked?
My wallet.dat is empty
Questions you need to answer.
1. Does anyone have access to your PC ?
2. Do you keep your wallet live or offline?
3. Any people you know in real life that know you are into Guldencoin?
4. Was your passphrase complex? Did you type it each time or copy and paste it from a file?
5. Did you have any errors in your wallet when you opened it?
6. What OS are you using. Mac is normally very secure but Windows might not be depending on what other software you have.
7. Other wallets you download might be used by coin developers and hackers to get access to your machine.