If all your efforts to find the cost basis fail, in the end you many just need to make a good faith estimate of when the shares were purchased, and research online for a stock price on that date or within a particular date range.
When don't have original transaction confirmation, you need to make an educated guess as to the cost basis. Otherwise, the IRS will presume that the cost basis is zero.
If you can make an educated guess as to a date range in which the shares may have been purchased, you can use historical prices at the start and end of that range to compute an average stock price for that time period.
Be sure to keep a record of this calculation, stating your assumptions and the figures used. It's possible the IRS will want to know where the basis came from.
Please see the TurboTax Help articles How do I find a stock's cost basis? and How do I find a stock's cost basis if I don't know when it was purchased? for research possibilities.
@Bayhill26
