The thing to realize is that DNA science is new and quickly evolving as more people test and the science gets better and more granular.
As such it was identified a couple years ago that Haplogroups need to be fairly often revised as new discoveries are made. The last major update was in 2014, and K2B2 used to generically just be K-M526.
Although K-M526 was previously characterized by a single polytomy of eight major branches, the phylogenetic structure of haplogroup K-M526 is now resolved into four major subclades (K2a–d). The largest of these subclades, K2b, is divided into two clusters: K2b1 and K2b2. K2b1 combines the previously known haplogroups M, S, K-P60 and K-P79, whereas K2b2 comprises haplogroups P and its subhaplogroups Q and R.
I have the same issue on YSEARCH which just has the top level Haplogroup and not the more granular one, that is it doesn't define my very specific CTS Haplogroup or even a couple levels above it and I have to use the generic R-M269, the reason I mention this also is that ISSOG's site shows the Y Haplogroup Tree is revised YEARLY.
I know the mtDNA Haplogroup tree was revised in at least 2009 and 2014, but possibly other years as well.
So until Mitosearch.org updates the available choices use the most granular available, so in your case as of 06/25/2015 use "K2" not just "K".