Grr. Not enough information to work with.
Lounge is a forum, so your posts are known as messages.
Your message list is
Latest Messages[
^]
You may remember the date and/or the subject.
And then there is the search facility:
Search[
^]; this one is limited to Lounge; check "just my stuff" and type one or more keywords (warning: default is OR operator, CP isn't Google!)