Ran into this problem today and didn’t see any info about it online. ESX stores the IP address of the vCenter that manages it in the HostConnectInfo object.
If you connect to ESX you can call QueryHostConnectionInfo on the HostSystem object to find out which vCenter manages it.
Here’s PowerCLI code that will do that.
Get-VMHost | Get-View -property Name | Foreach { $_.QueryHostConnectionInfo() } | Select ServerIp