Have you tried the advanced search options page (
link)?
You can add a few restrictions to make it likely that you will find your post. Put in your keywords, put your name in the
Filter by Member Name box and check the
Match Exact Name checkbox, change the
Search posts from... dropdown to 180 days and choose the
Newer radio button, and change the
Result Type option to
Show results as posts. Perform the search, and you should get a listing of posts you have made in the last six months that match the keywords you have specified.
Give it a shot.

Mike