The seller cancelled all the bids first, then
cancelled the auction eventually.  In the
page, he explained "Checking authenticity".  He
probably got a notice from someone else that the
cel is probably not the production one.  As you
may or may not know, the studio that created
Ah! My Goddess, AIC has created a bunch of decent
quality of "re-production" cels many years ago.
Some of them are pretty nice and hard to tell 
which ones are used in production, which ones are 
re-production cels.  Anyway, the seller did this
as a preventive measure, so he can check the
authenticity of the cel whether it's production
one or not.