I have never sent a text, email or called a WG to say thank you.
I have however had texts FROM them, thanking me.
Not sure where this rule about never seeing a WG more than once, comes from, its fine to see a WG regularly if you hit it off, but if it goes a past the working relationship, then run!!!!!!!!! I had a girl who decided to tell me her real name, she asked mine, I told her a lie and never saw her again. Mind you I never heard from again either.