I don't know. I don't think it happens often.
I rewrote the partial once to make it more like my pitch, and then after that, she asked for the full. I sent the full, and she wanted me to 'speed up the front end' so I did.
She rejected me and said that the plotline was too confusing. I was *terribly* disappointed because they are such a HUGE agency and I'd worked with them for so long (months and months). And to come that close! She'd even called me to discuss rewrites.
I guess in the end she didn't think she could sell it.
I've heard of other people having similar situations, but it usually does end up with acceptance. I'm just the lucky one. *g* (Either that, or my manuscript is that awful)
And fingers crossed on this end here!