Qestion on Phone Warranty

We have a Siemens S66 with Cingular bought last June. We have been having
intermittent problems with it randoming shutting off 7& been getting worse
..So I called warranty exchange & they sent out an exchange phone which
arrived today.
I just noticed that the volume button on the phone side is missing. I am
sure that this has nothing to do with the problem we had but do you think
that they will say the phone is physically damaged & charge me $210. They
read that I could be charged up to that if I didn't return the phone within
10 days

I have seen on eBay some dummy phones. would it be worth getting one of
those to pry off the button & replace it one the other phone before sending
it back or just send back the replacement phone and not do anything.

Thanks,

Barbara L