Why mirrored mesh doesn't work in game? [SOLVED]

I edited an eyelash mesh, because it wasn't at the right place. I deleted the right one, and edited the left side. When I finished, I used Mirror modifier, and in blender and s4s it looked fine, but in game the side I deleted still was at wrong place.

I tried delete right one again, and duplicate that one I edited in object mode, and mirror in edit mode, then join them, but the result was the same.

Here is the blender file I edited.