Serial Number on a Stolen LifeProof Case?

So around Christmas time last year, one of my friends gave me a LifeProof case for my iPhone. He said he recently bought it for himself, but ultimately decided to give it to me as a gift since I had been wanting one. He gave me just the case, no box with it, and no receipt, which didn't really matter to me since all I needed was the case. Well now, about 7 months later after using the case pretty much the whole time, I took my phone into a water park to take some pictures while on some of the water rides, and water somehow seeped into the case and made my phone stop working (which is now sitting in a tub of rice to dry it out.) I contacted LifeProof and told them the situation, and in order for them to replace the case they need a picture of it with the serial number. Now I'm a little worried that the case may have been stolen because I learned my friend used to do that, so I'm afraid of sending LifeProof the serial number. Will they be able to tell the case was stolen, and would I get in trouble?