Glad to hear you didn't run up any penalties...
The bummer about the situation is that the IRS spent our tax dollars to audit you for no reason... maybe it is time for a new algorithm?
Your advice is right on...
As a tax preparer I've seen my share of IRS audits and from my experience you're guilty until proven innocent. If you don't have documentation of that deduction on your return... You pay the consequences. It's that simple.
I read somewhere that the IRS is increasing audits of individuals 30% from last year, so don't be trying to cheat Uncle Sam unless you're willing to pay the consequences...