A nasty experience with "the currentcard"

[Geoff Canyon]

It seems currentcard is undocumented. I don't even know where I came up
with it. But it works in general:

    put the long id of  the currentcard of the topstack

works fine in the message box. It also works in the script of a button --
generally. As it turns out, the above will give an error *if* the button is
in a palette stack, but not if it's in a toplevel stack. (at least in 6.7.1
on a mac) I can't really call it a bug since "currentcard" isn't in the
dictionary. But it just cost me two hours of my life, so this my primitive
yawp of frustration.