How do I reference a resource created in a bicep file that shares the same parent main.bicep file?

I have three bicep files…

main.bicep

module ddosProtectionPlanModule 'ddosProtectionPlan.bicep' = {
  name: 'de-ddos-qa-01'
  scope: resourceGroup('00000000-0000-0000-0000-000000000000','QA-01')
  params: {
    name: 'ddos-qa-01'
  }
}

module vnet 'vnet.bicep' = {
  name: 'VNet-dev-01'
  params: {
    ddosProtectionPlan: ddosProtectionPlanModule.outputs.ddosProtectionPlan
  }
}

ddosprotectionplan.bicep

param name string

resource ddosProtectionPlan 'Microsoft.Network/ddosProtectionPlans@2021-05-01' = {
  name: name
  location: resourceGroup().location  
}

output ddosProtectionPlan object = ddosProtectionPlan

vnet.bicep

param appTitle string = 'test'
param environment string = 'Dev'
param ddosProtectionPlan object

param vlanName string = '${appTitle}-vlan-${environment}-99'
param location string = resourceGroup().location

resource virtualNetwork 'Microsoft.Network/virtualNetworks@2023-11-01' = {
  name: vlanName
  location: location
  properties: {
    addressSpace: {
      addressPrefixes: [
        '10.70.0.0/24'
      ]
    }
    enableDdosProtection: true
    ddosProtectionPlan: {
      id: ddosProtectionPlan.id
    }
  }
}

resource subnet_01 'Microsoft.Network/virtualNetworks/subnets@2023-11-01' = {
  parent: virtualNetwork
  name: 'default'
  properties: {
    addressPrefixes: [
      '10.70.0.0/24'
    ]
    serviceEndpoints: [
      {
        service: 'Microsoft.Storage'
      }
      {
        service: 'Microsoft.Sql'
      }
    ]
  }
}

output virtualNetworkObject object = virtualNetwork

However when I run the main.bicep, I get the following error in Azure…

The language expression property ‘id’ doesn’t exist, available properties are ‘apiVersion, location, properties, condition, isConditionTrue, subscriptionId, resourceGroupName, scope, resourceId, referenceApiVersion, existing, isTemplateResource, isAction, isExtensibleResourceReference, provisioningOperation’.