This is exactly what happened for me when the Cardiff stopped was moved - new ticket automatically issued for the same coach with the same timings, but a different stop.
I assume these updated tickets are issued automatically, and perhaps that system hasn't worked properly for the OP, but with the poor customer service, they don't know if that's the case or not!
Thank you to all who have responded. Flixbus are still selling seats aboard a 2320 Swansea TO Bristol service in September but Markymark2000 has alerted me to the change of destination stop. As others have pointed out, in similar cases a change of stop can easily be addressed in issuing an amended ticket but for some reason I have been denied that option with a 4 hour delay overnight being the result. I have tried daily contacts to Flixbus but they are just ignoring me. Their sole reply, days ago, states:
Please note that due to operational reasons the time of the departure needed to be changed. As states in our T&C we have the option to amend the departure time if this is required or caused by unforeseen circumstances.
but clearly that is untrue since they are still selling tickets for a 2320 Swansea departure, as per my original booking.
So I will be likely be sat waiting in Swansea at 2320 and witness a coach that will depart 2320, only I will be denied travel on it, despite having booked to travel months earlier!
As for "unforeseen circumstances", surely that cannot apply when posters on this forum were previously aware of a change of Bristol stop, so Flixbus must have had to plan this some time ago.
The August Flixbus Bristol stop is just a few minutes walk from the September onwards Bristol Coach Station stop, so would legal restrictions be so severe as to totally cancel a booking? This is so unfair and seems to deny UK Consumers fair and honest treatment.
Thank you all again, for your comments.