April 11 had an accident with semi truck made report with plate number with hit run unit?

det. told me that the plate was to several trucks and not a semi and that it had not been reg. with the license bureau and he could not help me. i had ins. on the car i was driving not mine, but i know if these plates were to several different trucks then they had to have been regristered before and a name goes along with them, but the det. would not give me nothing except for telling me they belong to several trucks. how can i narrow this down to the driver that hit me from behind, i know what he looks like as well