I noticed the question on another community today. The "sore thumb" beat does not look like a PVC to me. It's preceded by a P wave with short PR interval. And it's not premature, it has the same coupling interval as the other beats. Also, you can see slow ventricular activation (delta wave) on the "weird" beat.
I remember a cardiologist on a forum once said that such beats may possible follow another pathway between the atria and ventricles (even if not all beats do so). I'm not sure this is the case here, but the original poster should ask his cardiologist in my opinion.
By the way, there are a number of pre-excitation syndromes. WPW is perhaps the most popular, and I think many people often refer to Supraventricular Tachycardia as WPW, like Kleenex to tissues. I had one called Orthodromic Circus Movement Tachycardia, a close relative to WPW in the AVRT family.
Every QRS complex of my EKG displayed a slight delta wave indicative of WPW. So, a one-off event? I'm gonna say, No, this isn't WPW.