Eugene, Does your car have a conventional chassis number, eg TS60,000L or TS60000LO? Standard Triumph sold some cars abroad as parts with assembly required. Many of these went to Belgium for assembly, as did my Triumph Herald. From what I've been told, build records for many of these cars are unavailable. They are identified by commission numbers though with prefixes such as "20" or "CKD". Others have an N or a b prefix. See Bill Piggott's, book Original Triumph TR2/3/3A p.109 for more on this.
I'm not suggesting that you's is one of these cars, just that the records for them are difficult or impossible to find.
If you do have a conventional commission number, it does not seem unreasonable that a few might have gone mission over the last 60 or so years.Tom