Sorry, that won't work.
The post office has it's written regulations and 
getting the cel appraised won't do you any good, 
cause the postal workers don't care.  Everything 
needs to be done simply and by their rules.  
Fill out the form for what you paid for the cel, 
NOT for what it's worth.  You will need to provide 
a signed receipt from the seller along with the 
insurance stub in order to get a refund.  And the 
only way you are going to get around not handing 
over the cel to them (which will be destroyed by 
them) is by slight of hand or fast talking.  What I 
mean by slight of hand is for you to remove the cel 
from the packaging with out having the postal 
worker notice and what I mean by fast talking is to 
totally confuse the postal worker into letting you 
keep the cel.  BE NICE to them, because once you 
hand over the form to them (make copies of 
everything just in case!), you are at their mercy 
and remember, the people you talk to don't make the 
rules and neither do their blosses.

Good luck!  ^_^