Non-Marketable Assets and 1099-Rs

[b]Background:[/b]
An individual owns a non-marketable asset in their IRA. Between 14-16 years ago that individual sells their non-marketable asset and deposits the proceeds of the sale into a retail (non-IRA) account. This sale is not reported to the IRA custodian and, subsequently, the asset continues to be carried in the account for the 14-16 years after the sale, with no distribution having been reported.

[b]Question:[/b]
How should the reporting now be handled?

Normally in this situation, a 1099-R would be generated for the amount of the proceeds not deposited into the IRA in the year of the sale. In this instance, however, it has been 14-16 years. Should an amended form 1099-R be issued for the year of the distribution? Or, should a 1099-R be issued in the year the custodian is [i]notified [/i]of the distribution? Furthermore, is there a statute of limitations on amending 1099-Rs?