First of all, it seams REALLY strange for a person
to lose a *very* expensive cel (guessing it is
probably at least $200-300???).  Second, after a
careless act like that, I would be very weary of
dealing with that person PERIOD.

As it stands right now, there are 2 options you
can possibly take that would prevent you from
losing your money on this deal.

1).  Accept the other cel and request the rest of
your money back WITH the fees (or just ask for a
lower price ont he cel and that will compensate
the fee loss).

2).  Ask for a full refund.  If you used Paypal
for this transaction, then all the seller needs to
do is click ont he "Refund" link on the
transaction page and you will be fully refunded
with no fee deduction.  
(I personally would chose this option).

Hope you resolve this problem soon.