amazon ecs how to get similar items

I have recently added an Amazon search to my website and am having an issue getting the full response I need. In around 10% of my calls I get zero hits even though Amazon's site itself display numerous hits. Here is my call to their service:

results = Amazon::Ecs.item_search(query_text, {:search_index => 'All', :response_group=>'ItemAttributes,Images,Offers', :item_page=>’1'})

90% of the time the results I get back are just fine, but with any of the following query texts this search returns 0 hits:

hoover bag 440004496 type S

Citizen Women’s Stainless Steel Bracelet Watch 18mm EJ5850-57E

mope space pack iPhone 5

Yet when I go to Amazon.com directly and search on any of these targets I do get plenty of relevant responses.

What happens is Amazon displays, for instance, "Your search "hoover bag 440004496 type S" did not match any products" and then goes on to display "hoover bag 440004496 type S” See all 322 results…” and plenty of good, relevant product matches that I would love to display on my page.

You can see the results (or lack thereof) at my site, www.FastForward.menu

How do I get these helpful responses through the API? Preferably in the same format that any populated initial item_search response is in? Preferably in the same call as the initial response so I don’t have to write more parsing code?

There is a “Similar products” API call, but to do that you need at least one product to pass in, which I do not have. See here: http://ift.tt/1zR4rhX

How do I get this list of “similar” products through the API so that my Amazon searched don’t come up completely empty around 10% of the time?

I am sure others have run into this same question.

Please feel free to ask questions or to make suggestions as to how I can improve this question.