TheFind collects product data from many different sources. They accept data feeds (like you are submitting through SingleFeed), they crawl your site for information and they have affiliate relationships with many of the PPC shopping engines (Shopping.com, Shopzilla, Pricegrabber, etc) through which those PPC engines syndicate some of their product listings to TheFind.
If you've activated TheFind in your SingleFeed account, TheFind now has potentially three sources of product data to display: the data feed we send, the data they've crawled on your site and listings from your Shopping.com/Shopzilla/Pricegrabber campaigns (if you are active at those engines). A data feed should usually get precedence over crawled data, as it is more structured and accurate. However, if TheFind has syndicated listings from any of the PPC engines, they will usually list those first, as they get paid a percentage of the click-thru cost. In those cases it's important to remember that the clicks will appear to be coming from your Shopping.com/Shopzilla/etc account and not TheFind. Because your data feed submission to TheFind is free, and they don't make money off of those listings, they will not typically be ranked higher than the syndicated PPC listings.
It's still important to deliver a direct feed to TheFind so that you can guarantee 100% coverage of your product catalog. You may not be listing your full product catalog at the PPC engines (due to ROI/cost concerns) and so you want to send a complete feed direct to TheFind. In addition, TheFind can have sporadically change how/when they pull syndicated listings from the PPC engines or how they crawl your site. For this reason, you want to maintain a direct feed to them. See this case study for more information.
In order to check if your products are live, search for "yourdomain.com" on TheFind... ie: "bestbuy.com"
If you have recently activated TheFind with SingleFeed, note that it can take 1 to 3 weeks for your direct feed to be processed and indexed at TheFind.
Visit TheFind's crawler FAQ and general FAQ for more information.