There doesn't seem to be any further clarification as to what the "prescribed manner" is;Permit for trailer
(4) No person shall draw a trailer on a highway unless,
(a) there exists a permit for the trailer; and
(b) there is displayed on the trailer, in the prescribed manner, a number plate showing the number of the permit issued for the trailer. R.S.O. 1990, c. H.8, s. 7 (4).
Ã¢Â€ÂœprescribedÃ¢Â€Â means prescribed by the regulations; (Ã¢Â€ÂœprescritÃ¢Â€Â)
What legislation are you referring to? Highway Traffic Act makes no mention of "VIN to be displayed on plate".ManufacturerÃ¢Â€Â™s vehicle identification number to be affixed
10 (1) No owner of a motor vehicle shall drive or permit his, her or its motor vehicle to be driven on a highway unless the motor vehicle has the manufacturerÃ¢Â€Â™s vehicle identification number permanently affixed. R.S.O. 1990, c. H.8, s. 10 (1).
(2) No owner of,
(a) a trailer that has a manufacturerÃ¢Â€Â™s gross vehicle weight rating exceeding 1,360 kilograms;
shall draw or permit the trailer to be drawn on a highway unless the trailer has an identification number permanently affixed. R.S.O. 1990, c. H.8, s. 10 (2); 2009, c. 5, s. 4.
As long as the VIN exists in some non-removable manner upon the vehicle(trailer), in some location, it would seem clear and obvious that you are not in violation.