I had that happen too, in a grocery store, many moons ago.  Hit both of us really hard...that look... as we stared at each other for a very long moment.  Then we went our own ways.  I checked out, but was still reeling, and went back in the store looking for him, but never saw him again.  I spent the next several weeks at that store hunting him.  Missed opportunity that I still regret today, at least 25 years later.