Think of the ablation as merely a road block across the highway. The road is still there, but the barrier prevents traffic from going either way. As Michelle indicates, over time that scar barrier formed by burning or freezing tissue can be bridged to support conduction. In my 4 years with the forum, there have been a few people reporting the same symptoms as you. My SVT was an accessory path AVRT similar to yours. It was in the left atrium down near the valve and supported conduction very well. After three years post ablation, I still get short little runs of SVT occasionally. I assume there remain a thread of conductive tissue remain which was missed during the procedure.
There has been over a decade of advancement in the field of electrophysiology since you underwent yours. I think it's worth your while to visit an electrophysiologist and see if a second procedure might be in order.
It might not necessarily be your wpw. I get little runs of ectopics from time to time. I had avnrt. It doesn't feel the same and it never lasts but a few beats so you would need to get it captured to see if your wpw is really back. The thing is as a young person there is a higher chance of it coming back because your body has a higher chance of being able to heal the scar so you may need to get it repaired again. If you think you can catch what is going on with a a 30 day event monitor it might be worth trying to catch so you know what you are dealing with. If it is plain old ectopics and your heart is otherwise healthy then you have nothing to worry about but if it is your wpw coming back then you can address that as well. Try not to worry though, just be mindful and watch stomach issues. They seem to be the biggest trigger for me getting ecotpics. Best of luck getting it sorted out and keep us posted on how you are doing.