Best Buy or Apple Service Broke My Phone

About 3 weeks ago my iPhone 7 began experiencing what I believed to be the "No Service" bug on iPhone 7 devices have experienced. Apple has been repairing that error under warranty when you send your device in.

I made an appointment, dropped off my phone at Best Buy (an authorized Apple Service provider) in perfect working condition (minus the cell signal issue), I am the sole owner, this phone has been in a case since it was purchased and has NEVER gotten wet.

I contacted Best Buy after about a week, they told me that Apple found water damage and it would cost $319 to fix! I was upset, I'd always been exceptionally careful with my phones, and felt that if I brought the device directly into Apple I could talk to them about the issue and have it resolved.

I picked up the phone from Best Buy this morning, the home button is functioning, but the Home Button is no longer working!!! I spoke with Best Buy, several times, and they are unwilling to make this correct by replacing the phone, they are adamant that it is not their fault and they want to resend it to Apple

I plan on going into Apple to see what they say, but I am concerned that I am going to be stuck between these 2 parties with everyone blaming the other.

Any thoughts or suggestions?