Dormant accounts query

I recently transferred money into a Permanent TSB account that has not been used since 2003, just to hold it for a few days before putting it elsewhere. I got a call from the bank saying the account was dormant, and that I needed to go into the bank with id to reactivate it. Same day I happened to be in BOI and the women ahead of me was having problems as her account had also become dormant, even though she had used it a few years ago - they were not allowing her to take moeny out. Question is this: The government legislation says an a/c becomes dormant after 15 years. How do the banks justify claiming an a/c is dormant after 6 years, and not allowing me transact on it, even for a short period? Why did they not send me a letter notifying me (there was over 1000E in the a/c originally - what if I had needed it urgently)? And if they don't mean dormant in the same sense the legisilation means it, why don't they use another phrase (such as 'Inactive account'/'Suspended account' etc).
Thanks.

I think it depends on how their computerised system is set up. I received a letter also from a building society that my account was dormant and when i enquired into it it was suggested that i add a euro to the account - so that the system recognised this as a transaction. If there is no transaction for a period -3 years in some cases - an automatic letter might issue. It can be a nuisance.