From reading past issues of their journal I know that Jersey have had some sporadic issues with the free ranging tamarins going AWOL on occasion and this mostly ended up with them returning but I remember reading that one or two may have been killed by cars and one apparently died of hypothermia (believe this was a pied too).
Yes, the wasting syndrome in Callitrichids is an awful phenomenon and really badly impacts pied tamarins in particular, good to hear that it was given the best of care though.