Did the participant not get a copy of the amortization schedule? Did the participant not get quarterly or annual statements with the loan balance?
I would not say the fault lies entirely with the plan sponsor.
Who did the year-end reconciling of the plan? TPA? Bundled provider? Someone should have seen this person was really behind at the end of '09. '10 the latest.
We would do two separate allocations of the gain/loss (thru 9/30 and after 9/30), but maybe/probably just show the net total on a yearly statement, especially if no one else got a 9/30 statement. I do not believe it would be appropriate to allocate the remaining gain for the full year, carving out the physician. A val date is a val date and once it is passed that's your new beginning balance for the next period.