A few different ways to check whether there is a ticket number associated with the PNR:

1. BA app, clicking on "View and manage more flight details" and ticket number should be near the bottom

2. You can use CheckMyTrip if you have or want to register for an account

3. If you have an e-ticket receipt email from BA it should list a ticket number if it's been ticketed

4. If you modify the booking through QR's website (change a contact detail), they should send a confirmation email soon afterwards. The ticket number would be listed under the passenger name in the email if there is one.