While helping out on a SEDE query here I was looking at the votes table in the MathOveflow database, specially the records for votetypeid = 8.
I noticed that the bountyamount isn't present in these rows prior to 25 june 2013. I presume this correlates to the join date of MathOverflow as an SE 2.0 site to the network.
Strangely enough the votes.votetypeid = 9 (BountyClose) does have a populated BountyAmount field prior to 25 june 2013 so it doesn't look like this data was missing.
Is this a data import issue and can this be repaired? If this can't be repaired I would appreciate to learn how I can reconstruct the bountyamount for a BountyStart, specially when there is no winner or when only half of the bounty is awarded.