How did it go? More than 120 days since you posted your question.
The SS approval letter takes weeks, months after an offer is submitted and seller's agent pushes and pushes the lender to make a decision and, the closer to list price, the shorter the time to approval.
You may mean the owner's letter indicating the lender will entertain a short sale, based on a completed application and owner's hardship. All that lender scrutiny and investigation is not begun until a qualified offer is made. They would then order an appraisal to see how much they will loose, if any. You hope the agent knew what they were doing when they priced the house, close to its value so the lender will not delay an approval. Many offers are far below the value that the lender either does not respond or counters with a reasonable offer based on their appraisal. Tell us what happened.