Did he have any explanation as to why Prosper doesn't report losses?
Apparently they do report losses now. On my 1099-B, whereas all my recoveries show a sale price alongside a cost basis of "-", my lone charge-off in 2011 shows a sale price of "-" alongside a cost basis.
Furthermore, I realized that the one loan for which I previously thought recoveries weren't reported on the 1099-B were actually subtracted from the cost basis, as it was the same loan that charged-off in 2011. So Prosper wasn't failing to report recoveries on a loan as I had stated earlier in this thread after all.
So, the only question I still had for Prosper when I left a return voicemail was why the numbers listed on the 1099-B are a few pennies off what is recorded on the Account Transactions page. Not really that important, but I asked anyway...