sp_helpdb is showing that nothing (other than allocation pages) has been created on the 'data only' fragment. [allocation pages take up 1/256 of pages in db, leaving 255/256 pages for use so: 10240 * 1024 * 255 / 256 = 10444800]
As long as you're still seeing free space = 10444800 you could try the following to get this fragment to show up as 'log only':
==================
use QAS
go
-- drop the default/system segments from the fragment
sp_dropsegment 'default',QAS,QAS_log_001
go
sp_dropsegment 'system',QAS,QAS_log_001
go
-- at this point you may get a message that no segments are defined on the fragment;
-- this is expected and can be ignored
sp_extendsegment logsegment,QAS,QAS_log_001
go
==================
Even if free space < 10444800 you could still use this method but you'll end up leaving some default/system segment data on the fragment. While this won't hurt database operations it does strand that data on the log device until the data can be moved (which is a whole other post).