You may well ask Graham. Sadly more Wyverns were lost over water than over land, making recovery more difficult and expensive. And coupled with the fact that Me’s and FW’s are more highly prized and valuable.. not to mention being more manageable size wise as well, its easy to see why the latter have a better chance of making it back onto terra firma than say a lesser known type.

But having said that this particular one was partly recovered with originally good intentions, but, for various reasons that have since been discussed in depth on this thread, was distributed to the four winds and in some cases scrapped with little regard for future preservation.
Yes frustrating but also true!