Unless a survey map is certified in YOUR name, it is very unlikely any legal issues/liabilty can be remedied against the land surveyor- you are on your own. If you have a large or complicated addition it may also be worth having a professional surveying company help layout the addition and check footings and/or foundations before construction proceeds to completion.
You can also pay to have a new survey drawn. This typically costs 225-300 dollars.
It is a necessary element to getting that building permit, so I advise you to find the survey you got at closing when you bought the house, or hire a surveyou and build it into the cost for ground breaking.
I hope this is helpful.
I am adding an additional suggestion to the ones below. Many times your lender keeps a copy of your "plat". You could try to give them a call.
I hope this information helps.