it isn't a level script though...
You'll have to add a level script to the map, separate from your script, in order to set the flag as soon as you enter the map.
You'd only need a simple script like:
#dynamic 0x800000
#org @start
hidesprite 0xY
setflag 0xZZZZ
setvar 0x7000 0x1
end
And it should mean your person will then appear when you showsprite + clear flag with no extra hassle.