Not a good place to be.

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If you've already removed the trim around the sides and back inside the boot then you just might have a chance through the indicator lens with a coat hanger tool and inspection camera if you've got one.

This lens will come off from the outside

( the end triangular one, just levers/pulls off) and if you then remove the rubber grommet around the wiring leaving a hole of about 40mm dia to go through.

The other rear light lenses won't come off though as the top screws are hidden by the boot lid.

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If all this fails and you don't want to risk damage to the bootlid or rear panel, then you might have to cut an access hole in the boot floor after removing the silencer, heat shield etc.

Best of luck!!!