Trailers are interesting. Its a major item in units, very much accountable. But real control of them is a bit thin. Yeah, we lock em up. Or lock the motor pool, Or place guards around them. But when you "lose" the Data plates, you are simply out of luck. The short answer is, no. There is no other number stamped on the trailer to help you I.D. that trailer. I found this real hard to believe.
I was once tasked to inspect and inventory ten M200A1 trailers. There were 3 Missing data plates. So I went and found a TACOM guy and asked him. He explained to me that indeed, there is no way to I.D. a trailer if the data plate is missing. I told him, "Trucks have additional numbers stamped on them, why not trailers?" He smiled and told me, "Cause they aint trucks." I folded my cards and went away.
Two years later, same deal, different unit. The brand new Motor Officer wanted to make all the junk trailers they brought back from down range look good. Most were missing data plates. So I took the young Lt. to the TACOM office and we asked the question again. Got the same answer, just worded nicer. I still find it hard to believe.