I may be wrong, but I assumed the reason it dropped out of sight was a licensing problem, what with the Die Cast being available & all.
R&D Unique was started by Dave VanDerwal in the early 1980's, concentrating on doing fine-quality white metal aftermarket model car parts of all kinds. His first foray into resin was a series of antique gas pumps that he himself mastered--then in the late 1980's, R&D Unique bought out Mini-Exotics who were located just over the border from Seattle in British Columbia.
In the late 1990's, Dave VanDerwal sold R&D Unique to the man who was doing all the resin and white metal castings, Tony Willing. This sale included not only the business with all equipment, but also all mastering. Tony Willing continued the business until a divorce entered into the equation, at which time he closed it, until the divorce is settled.
That is pretty much where it stands today.