Hi I am so sorry to hear that. Hope it turns up. Please see the link, - 'how to value gold in six easy steps' in the Jewelry Resources. This is why i stress to guests who visit this site, the importance of appraisals.
Did you keep a digital record, do you have an image of the ring? Do you know the size, it is possible, for a jeweler to work out the weight if you knew the size of the ring; you did mention the width of the band. Was it hallmarked 18K ? Is it plain or was it set with stones? Apart from the gold store of value you have the antique store of value, that involves the craftsmanship, the complexity of the antique gold work that went into its making. Of course you cannot determine the loss, the sentimental value in financial terms.