So I just bought my Adidas Coogan backpack yesterday at Marshalls and I haven't taken the tags off yet I still have the receipt and I was wondering about their lifetime warranty; does the warranty work even if I didn't buy my backpack from Adidas? Because I have to keep this backpack for junior and senior year of high school and if something happened to it would the warranty be valid? also do I need to keep the lifetime warranty tag? I know I have to keep the receipt (even though it's from marshalls).

Please help me.