I know Crewella experienced something similar but from another seller (the whole thread is here:
http://bobthepleo.com/forums/index.php?topic=1884.0)
Belle came from Gimmedigi. I did feel the box had been opened, and the battery arrived fully charged, but Belle had definitely not been hatched. I also had an issue with the code sticker having been obviously peeled off another page and stuck into my instruction book, although the serial numbers all matched, and the code came up as invalid when I tried to log into the Pleo Profile on the Hong Kong Pleoworld site.
Having said that, Gimmedigi shipped quickly, responded to my queries intelligently and solved my problem in good time, and overall I'm very pleased with Belle and have no wear issues.
But the numbers matched on hers.
Also, you said the box was green right? Do you mean the dino on the box or the box? My 2009 Pleo had a green box but my RB had a white box. Although the coloring of the eyes sounds like an RB but figured it can't hurt to ask.
Do you have pictures of your Pleo and the box etc. that you can post by chance?
I'm not 100% I'm visualizing your battery problem right but it should look like this once it's inserted and the tab is back down:
Is the battery being put in right? (The little plastic nub [maybe this is the tab?] goes into the slot correctly when the bottom of the battery is lined up right?)

If you notice at the bottom of the battery there's a little plastic spot that sticks out, there's a corresponding spot inside the pleo it should slide into when properly aligned and then ideally it shouldn't sit much above the charging spot (it still requires a little push down and twist).