DID NOT WORK:
var %map.draw.trying = $scriptdirglobalgfx\ $+ $3
e $exists( %map.draw.trying )
WORKED:
%map.draw.trying = $scriptdirglobalgfx\ $+ $3
e $exists( %map.draw.trying )
NOTE:
The presence of /var is the ONLY thing that changed, for the offending routine to be successful. The given lines appeared exactly as I've shown you.

PS:
I just remembered that I also tried $isfile and $isdir through this trial, and neither did they return my results until I created a global variable rather than local... enlighten me

mIRC 6.17, win2k

Worked
on *:TEXT:test1 test2 test.txt:#: {
var %map.draw.trying = $scriptdirglobalgfx\ $+ $3
echo -a $exists(%map.draw.trying) <--
}
[06:38] <@mIRCManiac> ed say test1 test2 test.txt
[06:38] <@E|wood> test1 test2 test.txt
$true <--

Worked
on *:TEXT:test1 test2 test.txt:#: {
%map.draw.trying = $scriptdirglobalgfx\ $+ $3
echo -a $exists(%map.draw.trying) <--
}
[06:39] <@mIRCManiac> ed say test1 test2 test.txt
[06:39] <@E|wood> test1 test2 test.txt
$true <--

v6.17 WinXP Pro SP2

male var into !var see if that makes a difference, you might have a custom var alias? Becuase it worked fine for me.

Besides $exists, you are also using decrapated syntaxing:
$scriptdirglobalgfx\ $+ $3

should be:

$scriptdir $+ globalgfx\ $+ $3

If this solves your problem I don't know

Doesn't make any difference, as $*dir identifiers allow for strings to be appended to it. Although it is supposedly depreciated usage, I don't see it changing any time soon

I saw in another thread hes had this problem with a bunch of things, someone else (mircmanic or querty i think) also pointed out he likely just has a VAR alias, thats screwing things up.

Adding to Dave's post, maybe you indeed have a custom var alias. You can check this with //echo -a $isalias(var)
It will return $true if you have a custom var alias.