I used to email in those moments as a way to try and keep the fading connection.
Now I probably just sit with it and let it fade until next time, it hurts at times, I will feel sad/angry and just try to sit with them and see if the connection comes back when I see her next.
I also try to read like others have said and try to find the reasoning of these feelings through self help style books, and write to her! Either that or I block it all out, pretend it don't exist and busy myself with other things such as tv etc