****** exhaust

My car (astra opc) was installed with a downpipe and exhaust in 2014.The original exhaust was ****** by staff after telling them I would be back to collect it, I was told that it had been cut and thrown in the trash and that I have no proof of of asking for it.last year I was told that when a opc like mine came into the shop they would replace mine.please can you help me out with this matter as I need my original exhaust back. it's been 2 years and nothing is being done.