I say, with Allah's guidance: Zakat is not obligatory on wealth as long as it is not expected to return, because it is a condition for zakat to be obligatory on wealth that it must be owned completely in essence and in disposition, and this condition is not met here. Wealth that is not expected to return includes lost wealth, wealth that has fallen into the sea, wealth that has been usurped without evidence, a debt denied by the debtor for years and then acknowledged later among people, and confiscated wealth, which is what the ruler takes from his subjects without right. However, if it is found after years, zakat is only due for the year it is found, as mentioned in Sharh al-Wiqayah, p. 208, and Allah knows best.