I'm not sure about this one. But it could be a case of the varable is not populated in the source code directly, but later inside of a javascript function call.
As for structure, I have two things.
The sort open tags '<?' tend to be a REALLY bad choice for cross platform compatibility. Sure it offers some nice things like '<?=' that's basiclly a quick echo statment with short tags turned on. However, this is very much platform depended, and not something you can turn on at run time. Avoid!
This seems to check if they are logged in via styles:
Code:
<vb:if condition="$show['member']">
<!-- Logged In -->
<vb:else />
<!-- Logged Out -->
<vb:if />