JeffT,
In a prior post I provided a link to the IRS publication covering cash contributions. You obviously have not been audited. You might want to review this document, as a little help you might want to look for this paragraph:
Contributions of $250 or More
You can claim a deduction for a contribution of $250 or more only if you have an acknowledgment of your contribution from the qualified organization or certain payroll deduction records.
If you made more than one contribution of $250 or more, you must have either a separate acknowledgment for each or one acknowledgment that lists each contribution and the date of each contribution and shows your total contributions.
The reason I point this out is that I know for a fact I have had to track down these receipts every year when filing my tax return. Now I make sure I get the receipts within 30 days of making the donations, makes tax preparation time a little easier.