Hi Etcetera!
I appreciate your hard work and dedication, Let me remind you that none of us have the magical potion or Cupid's Arrow for every problem. You'll have to take things with a little grain of salt, and continue to proceed.
I can see how some people would take advantage of this site, Especially 12 year olds that have nothing better to do then to masterbate and laugh at people's problems.
As for identifying a troll, this will depend on your overall experience and knowledge of the situation. If the Venter tends to go off the topic easily, and starts off the conversation in a very awkward manner; Such as:
"Hi, I'm Joe... I divorced my wife, I beat my kids with a metal pan... and I'm currently drinking excessive amounts of alcohol to solve my problems"
It's very clear to tell something's very "Fishy" about the situation. Some maybe harder than others is what I'm trying to communicate to your understanding.
Overall, I think you'll just have to take it as it was mean't to be. Afterall this is the internet and you are prone to meet a troll every once in a while. Your best option is to "Flag/Repot" the individual and let the program guide you to the next available vender.
Best of Wishes!