Several cases of this type are recorded in the case files in NV. and believe it or not most of the collections have been recovered after the heir was able to prove that the buyer had knowledge of the real market value and took advantage of the sellers lack of knowledge. But being that your mother sold the collection back in 1997, it might be hard to track down the buyer and the collection. Oh well I guess in every life a little rain must fall. Truly sorry about your loss.
Hava Good Day,
Richard