I need some advise on a shipping disaster.

I recently purchased a pair of speakers on Audiogon.  The price I offered was accepted and I sent the payment promptly.  The seller in return shipped the 2 speakers promptly and sent me the tracking numbers.  One of the speakers was delivered the next day and UPS has lost the other speaker.  The seller has put in a lost package investigation however UPs has not recovered the speaker.  It has been 8 days since the lost investigation has started.
I come to find out that the package was only insured for only half of what I paid for the whole package and it would cost twice that to replace the lost speaker new. So even if UPS cannot find the speaker and pay the insurance claim I cannot even replace the missing speaker for the amount of the claim.  
I'm not sure how to go about solving this issue.  I purchased and paid for a full set of speakers and only have 1.  
Any suggestion on what I should do next?  Has anyone ever experienced an issue such as this?  Does Audiogon have policies around issues such as this?

Thank you,

Speakers should be insured for double their cost.I'm glad you got your money back

I bought a McIntosh MC2105, that was fully insured and packed very well by an independent pack/ship business. Insured to the full amount. Upon arrival, the front glass panel was cracked. With the seller and the shipping store assistance, we submitted the insurance claim to UPS. after about 2-3 weeks, we received an answer that it was declined. The shipping place resubmitted the claim, and after 55(!) days, I received a check for the total repair cost. They sure didn't make it easy though. 
Save yourself a LOT of difficulty.
If you paid with a credit card, either directly or via PayPal - 
contact your credit card company and explain that what you paid for has not been received. They will handle everything, after allowing a reasonable amount of time - you will receive a full refund. Returning the item will be the responsibility of the seller.
I went through this with an eBay purchase.
Always use a credit card when making a purchase just for this reason. PayPal and Audiogon policy do not provide buyer protection of major a credit card.