Second Mortgage Won't Accept The First's Approval

I am currently representing a Buyer client on the purchase of a Short Sale. The Seller's first mortgage is a Fannie Mae backed loan with Wells Fargo. The second is with US Bank. This is a traditional short sale, not HAFA.

Wells Fargo has issued their approval, with no Seller contribution at closing or promissory note. They have allocated 10% to the second mortgage, per their investor guidelines, and will permit no more - to the exclusion of additional funds/promissory notes from the Seller or the Buyer that those parties would be willing to bring to the closing table. US Bank has rejected these investor terms.

Now, you're thinking, "so what's so unusual about any of this?" What's my point?

My point, a question really, relates to the listing agent's ethical responsibility given this situation (per the Realtor Code of Ethics). Since the second mortgage has rejected participation in the short sale, shouldn't the listing be removed from the MLS? Or is it acceptable to let it languish, as part of an already bloated inventory, until it dies a natural death as an expired listing?

I'm looking forward to reading your comments. Please post!