According to the Utne Reader ("The Best of the Alternative Press"), Trader Joe's is, at the very least, "notoriously tight-lipped about where its store-brand products come from."
They go on to say:
A report on organic dairies from the Cornucopia Institute, a sustainable-agriculture watchdog group, warns consumers to be vigilant about the explosive growth in these sorts of “organic” store brands. Private-label organics like those in Trader Joe’s “seem to contradict what many thought the organic movement was all about: consumers understanding where their food comes from and how it is produced,” the report states. The Trader Joe’s brand of milk, for example, claims to be organic—but it won’t disclose which dairies it buys from. Ditto for the soybeans it uses in its brands of soy milk, tofu, and other products. And a recent report found that its store brand of veggie burgers are made using hexane-extracted soy protein.
According to Organic Consumers Association
Pat St. John, vice president of marketing for Trader Joe's West Coast division in South Pasadena, Calif., said the chain sources organic products whenever possible, and objects to being targeted by Greenpeace for selling GM foods, "when 60% to 70% of the food on anybody's shelf is likely to contain GMOs. "We don't carry, nor do we claim to carry, GMO-free products. It is a goal of ours, but due to certain standards, we are unable to guarantee it at this point," St. John said. "Trader Joe's is not going to
say we aim to do something that we are not sure we will ever be able to do. Regarding labeling, St. John said, "The state of the industry right now is very much in flux, and even well-meaning people are finding it very difficult. [For GMOs,] if the FDA, or USDA choose to mandate labeling, they will have to agree on what the labeling will be. To test down to the zero percent is impossible now.
So I'd say your instincts are serving you pretty well....