Wouldn't a Virtual Library name in bold italics on a wider button do that equally well.
For the record, my suggestion for title & status bars would be something like
Code:
Title : calibre version nn.nn.nn [nn bit] created by Kovid Goyal
Status : <library> (nnn,nnn) || <virtual> (nnn,nnn) || Search: nnn,nnn || Selected nnn.nnn
BR