There are several issues - how to identify the taxable gain from your investment; how to report the income; and
how to support your income and deduction in case of audit.
The first question was addressed above and so far it doesn't need any clarification.
As for the second issue -
A gain on a personal foreign currency will be recognized if the transaction occurred.
If the gain is less than $200 - it will not be a taxable income (see IRS publication 525 page 30 for reference - http://www.irs.gov/pub/irs-pdf/p525.pdf).
The gain of more than $200 is reported as capital gain on the Schedule D and on line 13 of Form 1040 - http://www.irs.gov/pub/irs-pdf/f1040.pdf
The section 988 provides that gains and losses from currency trades are treated as ordinary income - not long term capital gain.
The last issue...
first of all you do not need to send any supporting documents unless you are audited.
The IRS has some specific requirements for supporting documents - see for details the IRS Publication 552, Recordkeeping for Individuals - http://www.irs.gov/pub/irs-pdf/p552.pdf
If you would not able to provide such document - your deductions may be disallowed.
As you do not have any purchase records - you may need to find some supporting information what was the price for Iraqi Dinar at that time - and that would support your deduction. But you do not need to send any supporting documents to the IRS with your tax return - just keep them for your record.