[SalesForce] LWC renderedCallback not retrieving a wired record

I have a Lightning web component that is being called from a quick action custom button from a custom object record page. When the component is loaded, I need to retrieve the record so I can get a field value from it.

This answer says to use a wire with renderedCallback. I've tried it but the wire is not retrieving the record in the callback.

In my console logs, I see the correct recordId value in the callback, but the wired platoonEventis empty and the data is undefined:

in callback
recordId: "a1l0m000000IHxOAAW"
Platoon event: {}
Platoon event data: undefined

I've tried connectedCallback but that doesn't work either.

Is there an issue with the fact that this LWC is wrapped in an aura component because I'm using a quick action custom button?

Javascript:

import { LightningElement, track, api, wire } from 'lwc';
import { createRecord, getRecord, getFieldValue, updateRecord } from 'lightning/uiRecordApi';

import OCCASION_OBJECT from '@salesforce/schema/Occasion__c';
import OCCASION_PLATOONID from '@salesforce/schema/Occasion__c.Service_Platoon__c';

export default class BatchRegistration extends LightningElement {
    @api recordId;
    platoonId;

    // Get the platoon event record so we can get the platoon ID field.
    @wire(getRecord, { recordId: '$recordId', fields: [OCCASION_PLATOONID] })
    platoonEvent;

    /* Functions start here */

    // Initialize
    renderedCallback() {
        console.log('in callback');
        console.log('recordId: ' + JSON.stringify(this.recordId));
        console.log('Platoon event: ' + JSON.stringify(this.platoonEvent));
        console.log('Platoon event data: ' + JSON.stringify(this.platoonEvent.data));
        this.platoonId = getFieldValue(this.platoonEvent.data, OCCASION_PLATOONID);
    }

Note: I've also tried this but it doesn't work either:

@wire(getRecord, { recordId: '$recordId', fields: ['Occasion__c.Service_Platoon__c'] })
platoonEvent;