Think of a search as words not phrases.
So, if you search on a particular topic, or noun, every time that noun was used, the search engine generates a hit.
They might show up chronologically, but not necessarily a what you want.
Because posters are lower volume than topic nouns, it often helps to start with a poster that You remember replying, the less frequent, posters, even better.
If you put a phrase in quotes, it will search for that phrase and ignore instances of each word occurring independently. It can be a pretty powerful way to search. If you search for
site:www.doublegunshop.com “For 2 Inch Case Only” (including the quotes)
Google will find all instances of that phrase, while ignoring all posts that contain all 5 words, but not in a single phrase, in that order.