Purple basil requires full sun to do best and very well draining soil. It is not a delicate plant. If the wilting appears to be chronic, then the roots are starting to rot...and cannot deliver moisture to the top.

I agree the "very moist" soil is your likely culprit. Basil is a water-hungry herb but won't be happy with constant moisture. Allow the soil to dry out enough so that the top inch of soil feels dry before rewatering.

Here is a link that might be useful: The Herb 'n Cowgirl

Was the garden show under cover? If so the basil might have been raised in a greenhouse and not have been hardened off and is suffering from being put straight outside.