You can have Apple or an Apple Authorized Service Provider look up your system serial number to see if they can retrieve that information. Unfortunately if your system was a special Configure to Order, then that information may not be available even to an AASP. Likely only Apple themselves may be able to access that information for a custom configuration.
FYI, if you want an extended warranty, then only get the extended warranty through the product manufacturer. Getting a warranty through the store or other third party will usually result in using an unofficial unauthorized service center using any type of parts they want to use. Plus even if the service shop providing the actual warranty service is reputable, they will may not care to deal with third party warranty repairs because it ends up with the shop losing money in the end. Usually insurance for products is a waste of money. Just put those product insurance payments to the side & save them and wait until a product needs a repair. Chances are all those payments you saved will be enough to cover the repair of a broken product if the product is even still worth fixing. Usually those warranties have so many loop holes and gotchas, that you may never be able to use them.
FYI, now that you have had this unofficial repair and the system now contains a part that is not even correct for the system, Apple will no longer repair it for you (maybe if you can have the original part reinstalled).
I would contact the insurance company and complain about this repair to see if they will reimburse you for a new laptop now that this service center has mutilated your laptop and made it unserviceable by Apple. You can also mention how these 2018+ Macs will have certain features are now reduced since the T2 security chip and Logic Board have not been properly "programmed" to work with one another. If you have no luck there, then I would check out your local consumer protection laws to see if you have any options. You may want to consult with a lawyer, although in the end it may not be worth it as it may be less expensive to purchase a new laptop. If you purchased this insurance because the seller suggested it, then talk to the manager of that store about the mess they made here and see if you can get fully reimbursed for the laptop. If the vendor happens to be an official Apple reseller, then report the issue to Apple as Apple will be unhappy that they offered third party insurance instead of AppleCare+.
Also, with the 2018+ model USB-C Macs, unauthorized repair shops are unable to fully repair these 2018+ USB-C Macs for multiple reasons. Many times a technician who performs board level repairs is unable to get the necessary parts to repair the Logic Boards (this type of repair allows the user to keep using the original Logic Board). Swapping parts on these 2018+ USB-C Macs is also not a good idea since Apple needs to reprogram the T2 security chip for the replacement parts since each major part has its own part serial number. If this reprogramming is not performed, then some functionality may be lost (not entirely sure what will be affected). Plus Apple has mentioned this reprogramming is also meant to properly configure some parts such as the displays color calibration profiles. Unfortunately it is not possible for anyone to reprogram the T2 security chip since only an Apple Authorized Service Provider (AASP) has access to the online utility. Even an AASP is unable to reprogram the T2 chip using parts purchased from third party vendors or taken from other Macs. AASPs can only reprogram the T2 chip when the replacement part has been purchased by the AASP through their Apple service portal since the online service utility uses information provided by Apple to complete the reprogramming of the T2 chip (aka Logic Board).
I'm not real hopeful for you here. It may be an expensive lesson.
Good luck.
