Viola, definitely find a new dealer...
On another note thats happened to me once before too.
No idea where the bolts went but that plate was "flapping". I took it in for service under warranty because the car had a rattling noise going over bumps. Sure enough they put the car on the lift and found the two bolts missing.
My guess is they somehow came loose and fell off. Probably not torqued correctly.
Anyway, make sure you strap up torque your bolts correctly
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2001 Boxster Artic Silver / Black Interior
-GT3 Front Bumper w/ Lip
-Side Skirts
-Gemballa Exhuast and Cats
-O.Z. Racing 18" Wheels
--18X8.5Front 18X10 Rears
-Michilen PS Tires 225/40/18 & 285/30/18
-5mm Rear Spacers
-Porsche Door Sills
-H&R Springs
-Powerflow Intake
-B&M Short Shifter
-Pioneer Avic-F90BT Navigation
-Focal Polyglass 165VR3
-Alpine PDX 5 Amp
-Bose OEM Subwoofer & Midrange
-Audio Controld DQXS (DSP)