Thank you for your question about this loss.
Since you were a passive investor (limited partner), your loss of investment is considered a capital loss.
You may show this loss on your 2010 return when the loss was first evidenced as a total loss by the foreclosure process.
Because this is a capital loss, you may use it to first offset any capital gains. In addition, you can deduct an additional $3,000 per year.
Assuming you cannot use the entire loss in 2010, the unused portion carries forward to be used in 2011. Again, it first offsets your capital gains, then up to $3,000 additional loss can be used to offset ordinary income. Anything left over, and the process continues to carry forward.
If you never have any capital gains, you will use this loss up by your 34th year (at $3K per year).'
Do I need to amend 2010 and 2011
Yes. If you do not amend 2010, the loss cannot be recognized. It must be started in the year the loss is permanent and total.