I had actually discovered something similar on one of my spare accounts recently, but because they had limited handwraps on them on inventory and in the cache in the first place and it was a much more limited use toon (banking mostly, older stuff too), I never really took notice until I noticed I had a few collars on that toon instead of handwraps, but I would never have converted some of those handwraps to collars either so that finally gave me an in as to possible causes and thought of this topic.
The only thing I am aware that might be related to such an event, is something to do with the Druid class (as it's the only class that character ever was prior) and possibly reincarnating or crafting a certain way. But I have not had the opportunity to try and test out what combination of events may lead to such a change yet.
But unfortunately, even should I discover the cause of the problem, I'm not sure you can get the original Handwraps back. Any named ones might be possible to replace, but random gen ones might be harder to do for the CS Agents. And of course, any unique effects on them might not be on the new ones either.
In any event, Good Luck with holding the line.
J1NG