According to the logo usage documents at USB.ORG, there is no requirement to display a USB logo of any kind on a device that has passed compliance testing. There is, however, a nominal (in the grand scheme of things) fee to register to be allowed to use the logo after a device has passed testing, provided that the logo is used only in certain conditions. Those conditions dictate required sizes, colors, placements, and grouping restrictions. Apple mark their compliance logos on their cables/adapters in a very light grey. This color is not permitted under the Logo Usage Agreement. Apple place their compliance logos on the bottom surfaces of their connectors. This is also prohibited by the usage Logo Usage Agreement.
In other words, as I said, no logo is not a sure sign that the adapter isn't compliant.