Only way i think the Tickets can become invalid are if they were ordered over the internet. The owner of the tickets could call in and say he lost the tickets and being they have a record of what tickets were sold they would cancel the validity of the tickets. If they were bought from a ticket booth though i dont think there si anything they can do. First thing i would think is to ask and see if anyone lost a pair of habs tickets...but it would be hard to see who actually would be honest in claiming them. Just remember, your benifits are someones loss. Id hate to be the one with those tickets and lose them. Where exactly did you find them?