"The part is a foil shield to protect the display/touch assembly from EMI noise from the battery/SIP module blow it. Here’s a better view
The cut off segments (right side) are the connection point to the case (drain). Apple does not offer replacement parts.
As this point I don’t know if your watch is repairable or not. I hope you got your money back from this person as he clearly didn’t know what they where doing!
Shields are important! Maybe you can find a junker watch which you can salvage the shield from."
