The headlamp rim locates on two broad lips roughly 10 and 2 o'clock on the plastic surround. It's then held in place by a single self tapping screw located around 5 o'clock into a hole in a raised plastic block. Significant downward force may be required to locate.
It's therefore possible to miss locate it. Not saying that happened just a possibility. MMC currently also place a short length of self adhesive neoprene strip across the top of headlamp securing ring to tighten fitting of rim and/or prevent rattles. Was this present?
