where is the field to look for a forum participant?

Along with the info, that others have offered, if you have a thread, in which the desired person has contributed, just click on their Profile to the upper-left of the thread, and choose "Send Personal Message" (PM).

Good luck,

Hunt

Some of these could be helpful:

http://forums.adobe.com/thread/903540

You can type their name in the Ask a question box and you will get a list of the posts they have participated in.

http://tinyurl.com/77aac66

There are thousands of them (if not millions!!) in there so you need to know something about the person concerned.

Good luck.