I have imported vehicles from Europe and Asia and they were inspected at the port of entry and the inspector Did Not install any kind of sticker on the vehicle stating it was DOT certified.
If it was not DOT certified it would not be allowed out of the Port of Entry. If you could not take it back to the country where it came from, the authorities would cut it up and discard it and then will charge you for all the costs incurred.
This happened over 10 years ago with the Chang Jiang motorcycles that were being imported from China. They were assembled and did not have USA DOT tires
and associated items on them. They are now imported in unassembled so you can build them as a kit and install the required DOT items.
So my best guess is: If it is here in the USA and you have a State title
on it, then it should be ok.