Assuming, of course, that it even was an ET tube and not some type of multi-lumen airway.
When it comes to the airway, it doesn't matter what the tube is. It could be a Combitube, ETT, EOA, King or LMA. The EMS provider who is supposed to be trained for the device has an obligation to check placement.
If you say it is a Combitube, which can also cause serious damage, does not make you less liable if you fail to know what you are doing when attempting to secure an airway.