Ok just read the comic. Well shit. That was a surprise. I was really expecting them to kill Frost, but it seems they proved me wrong and just one more time proved. that there is no 100% guarantee. While I wasn't expecting Cassie killing Frost on her own, there was always possibility that someone could have forced her and I mean that possibility almost became true if not for Jarek and Tanya.
I am still thinking that this was just a nice fanservice and we might not see Frost in the future.
As for "abduction"... why pretty much everyone here decided that it was done with evil intentions? Maybe actually they were SAVED by the orders of Kotal Kahn? You know so to make Sonya owe him and make alliance? That is also a VERY strong possibility.