Property 'x' does not exist on type (when checking if it exists)

The relevant part of my current code looks like this:
(code edited from https://github.com/expo/expo-server-sdk-node)

  const tickets: ExpoPushTicket[] = [], receiptIds = [];

  ...

  for (const ticket of tickets) {
    if (ticket.id) {
      receiptIds.push(ticket.id);
    }
  }

where the types look like this (from expo-server-sdk library):

export declare type ExpoPushSuccessTicket = {
    status: 'ok';
    id: ExpoPushReceiptId;
};
export declare type ExpoPushErrorTicket = ExpoPushErrorReceipt;
export declare type ExpoPushErrorReceipt = {
    status: 'error';
    message: string;
    details?: {
        error?: 'DeviceNotRegistered' | 'InvalidCredentials' | 'MessageTooBig' | 'MessageRateExceeded';
    };
    __debug?: any;
};
export declare type ExpoPushTicket = ExpoPushSuccessTicket | ExpoPushErrorTicket;

The issue is if (ticket.id) gives Property 'id' does not exist on type 'ExpoPushTicket'.
The purpose of the if in itself was to see if the property id existed, since it's undefined only if there is an error.
I checked to see if there were other methods and found Object.prototype.hasOwnProperty which managed to not give a compilation error on the if line, but the error was still there on receiptIds.push(ticket.id).
What is the correct way to check if my ticket contains the property?
Should I import and change the type of ExpoPushTicket?

The type ExpoPushTicket is a union type. Without a type guard you can only access a property if it exists on all union participants. In your case check first for a specific type using a type guard and then access the id field.

The simplest solution is probably the in operator:

  for (const ticket of tickets) {
    if ("id" in ticket) {
      receiptIds.push(ticket.id);
    }
  }

This check narrows the union type to ExpoPushSuccessTicket where accessing the id field is legal.