The limited selection methods in Poser are definitely one of my biggest gripes with it.  The offending polygon may be behind or partially obscured by other polygons, which will make it hard to select in Poser. You may try changing to wireframe view and selecting the area, then deselecting any additional polys you may inadvertantly select in wireframe mode.

Hey! His nose is dry! ... Someone should lick it,  just in case. - Diego