I just lost a long time friend, Gyarados

Can anyone please help me. I was surprise trading in Pokemon sword and shield and accidentally traded my shiny male gyarados that i got from the event in 2020 i just want back my gyarados it upset me as soon as i understood what happened. Can someone please tell me they have an extra or something they can do to help me get back my lost friend he was level 63 with a calm nature