Either I can't recognize my dual, or duals aren't exactly the end-all be-all magical fairy pristine and perfect men and women sent to us by our Lord and Savior Jesus Christ as Auschra tells us they are.
My SO's an activator, though, which is like the silver medal in the Socionics world.
I thought I might have recognized my dual, but realized she was just as introverted as I was, so I figure its super-ego relations (sort of similar, but more problems, which of course, assumes that I'm not LIE, ILE, or even LII, though I absolutely abhor all ESEs).
I don't actually know any ESFps, so I can't say for certain.
Just to note... I don't think duality is always best (obviously enough). Based on circumstances and past history, among many other factors, people can be led to even more promising prospects. You cannot fall in love for the first time, every time... and so, the road to love is just as intricate as anything else in life. Evolution. Some things will be the same, some things will be different. What's more important is sharing common values, such that there would be mutual respect and compassion... that may ultimately lead to commitment (if that is also among a pairing's values).
I have interacted with 6 duals in my life. Two I outright wanted to punch in the face, one I actually took the time to "out wit" in hopes of making him feel like an idiot. I've never really felt compelled to do that to anyone before but he sure brought it out in me. They may have been enneagram 3s. Either way they were pricks.
The others were wonderful people and the experiences were all ones that I treasure. I think about them often in a way I don't think about other people. As an sx/sp I prefer to share intimacy from a distance - so lots of friends live abroad and I am happy to keep it that way - but they don't often linger in the back of my mind. These folks have and may always will.
It was like everybody is in black and white and they are in color. The initial physical rush you get is followed by this warming of the insides. Or that pesky yearning kind of stops feeling like acid reflux. ie, they are able to reach that inaccessible/never satisfied place.
I only kept in touch with one (a lot of them were military) who currently works in the Middle East but in the end I ignored his last email, missed him and sent one 2 months later and doubt I will hear back.
In hindsight I think I need to stick around a bit more when I meet my dual. I always assume (as usual) it was nice and kismet, back to my routine as he goes back to his.
As far as a relationship is concerned though, I'd only ever be with an SLE.
LSI's and I have a wonderful time but I don't think I could marry one. 90% of my circle were LSIs.
The way I whole heartedly miss the others, I whole heartedly still want to punch the other 2. Till this day.
I work for one right now actually. Really easy relationship and by far the best supervisor-employee relationship I've ever had. Funny because we're both e6. We seem to naturally speak each other's language and see the same things as important and unimportant. That said, I feel like socionics takes the "dual magic" thing kind of further than I think is realistic.