Turn on debug mode and see if vBOptimise adds itself to the drop-down of report items. If it does not, please try disabling all other mods (it's fine to turn your forums off for this process if you don't want others seeing this info, your page loads alone should generate stats) and see if vBO appears there then.
If it still doesn't appear (don't rely exclusively on the stat counter as it recounts every 10 minutes) then please PM me with a link to your issue post, an FTP account and an AdminCP account so that I can find out what's going on
Fillip