Are you sure you were selling for gains? You start your story with buying at the top. If you sold for losses we're talking about capital losses and you bought back in within 30 days you won't be entitled to those losses anyway.

How much did it go down from your original buy to your trading zone. It's possible that your original losses would exceed any smaller gains you had in your trading zone. And it's good of you to settle up, give it your best effort. Don't sweat it too much if you cant get this information back, the IRS isn't likely to chase you down, especially if your original losses would minimize any gains they could tax.