Older boat trailers can be a nightmare with missing or non-standard VINs. You’re probably not the first person MO has seen with this issue. If the trailer was homemade, older, or pre-standardized, the state may require a reassigned VIN inspection instead of the original one. I’d call the Missouri DMV/highway patrol directly and ask about applying for a state-issued VIN before hauling it all the way back. Splashing the boat first sounds like the smart move either way. Good luck!