after DM, i went to collect my complmentry voucher for some goodies and i notice i cant buy vodka,scotch or wine anymoe. I checked my notes and i had the codes ...... does this happen on purpose?

Alcohol vouchers don't seem to work outside the Sierra Madre. It's a known issue "The codes for making alcohol do not work on vending machines outside of the casino area. " http://fallout.wikia.com/wiki/Sierra_Madre_Vending_Machine .