Ditto what Steph said! It is most likely a coincidence and not related per se to the surgery. There would be no need to warn you ahead of time of a risk for AF, any more, for instance, that it would be necessary to warn you of the possibility of getting thrush from an antibiotic you took after the surgery. Things just happen sometimes! I also wonder why your PCP didn't refer you himself, and certainly I would seek out a cardiologist if I were you.
Boy, it sure does sound like she is giving you the brush off!! If there is one thing i can't stand, it's a doctor that can't look beyond the body part he/she is treating and treat you as a whole patient.
My experience has been (and i work as a physical therapist in a hospital, treating all sorts of post-op patients, but never vein ablation, as that is done as an outpatient) that any time there is an "insult" to the body, stress on the heart can result in A-fib. A stress on the heart could be an infection somewhere in the body (like pneumonia), or after surgery...being under anesthesia is not a "normal" condition for your body, and sometimes, the heart can get a little angry. So, it is possible that the procedure kicked you into A-fib. It is also possible that it is a huge coincidence.
I am curious to know, if you saw your PCP for the UC flare, and he diagnosed the A-fib, why didn't HE refer you to a cardiologist?? A-fib is not to be messed with...the blood thinner (if you are still on it) will help protect you from developing clots in the left atrium that can cause other problems like pulmonary emboli and strokes, but paroxysmal A-fib, over time, can become chronic, and the more you are in A-fib, the greater the likelihood you will stay that way.
Can you not see a cardiologist on your own? I would do that. Good luck.
steph