You could always try manually surfing to the location where you think the kernels are to check. I'm also guessing that your yum.conf contains lines with the following in:
These make Yum automatically fill in the urls according to the spec of your machine, so if your running fc2 on an i686 it'll make Yum look in the 2/i686/os folder for the RPMs. Since its a test release teres a good chance that the folder your after automatically will not exist. You could change it to look in the FC2 folders although Idon't recommend this.
On a side note however, why do you want to change the kernel? If the original kernel is the one which came with FC3T2 then you should stick with it as it is obviously the one intended for testing and reporting on in the Bugzilla