Reloading model error; same faces/polygons count

so i remodelled some element in multiple models of an project of mine.

on the left the old model on the right the new with much less faces/polygons.
(left the railing was to complex, so i remodelled those)

i have this old model in d5 ready.
but when i reload. the facescount is the same… how? do i someting wrong?
are the old polygons/faces in cache of the d5 render file ?

the reason i ask is i have a big project ans i optimized multiple building like this. i also use often ‘reload from local folder’