Bet you've never heard this one before

[think_tom]

I can't believe this. Thumbnail of the situation, I know you all have to return to making backlinks...
I'm buying a site. Neglected, 5.5 years old with 2400 posts, but very sporadic postings in the last 1+ year, only 2 posts since October.
Doing the domain transfer right now, money in escrow.
Despite the few posts lately, seller had 12 short posts in his 'drafts' part of the blog. He decided to publish them now, while he still owns the site. Why not? I checked and each of them were indexed by G quickly and brought traffic, as shown by Analytics. Cool.
Still doing due diligence and checking things out, and yesterday I went in and determined that six post were no longer indexed. I just checked again and now NONE of the 12 posts are indexed in Google!!
Wondering if 12 posts in 2 days being so far out of his normal posting pattern raised a flag, but to me it seems unlikely. This is not the 'honeymoon period'; the posts didn't drop in the serps, they aren't there at all anymore.
Any thoughts from anybody?