I've watched as the listings dwindle in many of my "regular" searches - sometimes it's just the market - people have sold off their stuff, and not much hits the market for some things. Other things are the "new or nearly new", and it's all overpriced/retail offerings (I wait for the rare BIN at the right price).
Keyword search can be a bit tricky to start with, but there are definitely problems with how eBay parses the search terms sometimes... you almost have to try a few random variations until you find the one that brings up what you were looking for sometimes.
There is a method some "buyers" (myself included sometimes) use - looking for commonly mis-spelt words, or variations of name or model #, and a few other little "tricks" to find "mislisted" items.
The problem I found with the "search engine" is if left to its defaults, it produces random garbage results (this is what the "average" buyer gets). You have to use "advanced search", and tweak it until you get a smaller and more accurate return. Even then, sometimes you get garbage, or a blank page, or an incomplete return... refreshing will USUALLY "fix" it when that happens, sometimes the servers hiccup.
When they say they have this great new thingy that will "automagically" serve up just what you were looking for, I have to laugh... silly monkeys! Not saying it CAN'T be done, but this lot of programmers and managers aren't going to do it!
WAAAY back they did a little contest to teach people how to search (may have been '06 or so?). They put up little "prize listings" with tricky but valid search terms, so they showed people HOW to search (fish) successfully.
Now they want to just slap a fish in your lap and go "this is what you wanted, right?" 90%+ of the time, wrong "fish"... their AI (artificial intelligence) algorithms just aren't that good at "shopping"!
