Welcome Carl!
I waited till others spoke;
SR blocks have been something of a curiousity to me, the fact that you have paperwork showing the block was replaced under warranty it pure gold as far as I'm concerned.
I have read it said here something to the effect that before a block would get authorized for warranty replacement, that the zone rep would see to the block getting irreparably destroyed.
This would make, to me at least, the odds of finding your original block, next to nil... but I agree, there is no harm in looking!
Let me see if I can find a good quote for you...
In the mean time, this link might be of interest to you:
Wallace Racing's Lost/Found Engine or Transmission Search