What happens if a country leaves the Euro Zone?

An article in the Financial Times compares a possible break-up of the Euro Zone with the period after the end of the old Soviet Union. We think that contrary to some observers Greece would not announce any date for the Switchover - it would all happen on one weekend, without any warning. Monday all accounts are denominated in Drachmas and Banknotes are stamped over. One little detail, what happens to bank notes circulating outside Greece that have been issued in Greece (all Euro notes can be traced to the issuing country). Whatever the likely disturbances, lower quotes for Drachmas would start a stampede to book holidays in Greece, buy property etc.