after visiting your site, it seems to me that your simple search form is somehow broken. I don't know if there are issues within v4.1.3 specifically or what, but if I execute a simple search for "caboose old style", I get 0 results.
If I execute the same search using Advanced Search, 10 results are found.
(Advanced) search works on your site, just simple search is broken, so I would check to see if there are any issues recorded in your error logs? Or maybe try to compare the actual form data between the Simple Search form and the Advanced Search form, to see what is different that is being sent.
I'm really thinking something must just be broken in X-Cart 4.1.3
I just ran the Advanced Search again, it executed fine, found 10 results. Then I clicked on "This Page Url", which supposedly posts the url used to find the search results, it came up with nothing.
http://www.sushob.com/shop/search.php?mode=search&substring=caboose+old+style &by_title=on&by_sku=on << 0 results
Check with X-Cart support, this may be an issue within the core. Or alternatively, if you have implemented any mods that intercept your URLs, or affect search functionality, try undoing those changes and see if search works