Praise be to Allah.
We ask Allah, may He be exalted, to compensate your loss and restore your wealth to you, and to compensate you with something better than that which was taken from you.
With regard to the zakaah wealth that you had earmarked to be the zakaah of your gold, then it was stolen from you, what is required of you is to give it again, because the zakaah did not reach those who are entitled to it.
Shaykh Mansoor al-Bahooti (may Allah have mercy on him) said:
If someone sets aside his zakaah, then it is lost before the poor person can take possession of it, then the owner of the wealth must give something else instead. End quote from Kashshaaf al-Qinaa‘ (2/269).
Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have mercy on him) was asked about a man whose zakaah became due, so he took his zakaah and gave it to someone to distribute it to the poor and needy. That man put it in a safe place, then it was stolen from him. Does he have to give zakaah again?
This money is still owed to the poor, because it did not reach them and it did not reach the one who collects it on their behalf, so it is still owed.
End quote from Majmoo‘ Fataawa ash-Shaykh al-‘Uthaymeen (18/479, 480).
The shaykh (may Allah have mercy on him) was also asked:
My wallet was stolen today, in which there was some money that I had set aside for zakaah. Is this amount of zakaah that was lost or stolen waived, or do I still have to give zakaah?
This money that the questioner had prepared for zakaah did not pass from his possession; rather it is regarded as still being in his possession and it has not yet reached those who are entitled to it of the poor and others. Based on that, if the money that a person has prepared for zakaah is stolen, then he must give something else instead.
Perhaps giving something else instead may be a means of Allah restoring to him that which was stolen from him.
End quote from Fataawa al-Haram al-Makki (tape no. 9, 1413 AH).
And Allah knows best.