Jim,
I search almost daily, so I would credit it to luck (and persistence) more than anything.
I use the search terms "paper model" and "card model" the most, then sort by category to get to the ships... Only every once in a long while will you see a unique ship model. Most of the time it's the usual stuff (GPM, JSC, MM, etc.) but sometimes you'll see a Watkins or other obscure model. But it takes tons of patience and daily searching.
Thanks!