sandvika: Photos kindly taken and sent to us by Håkan & Lina show they found the correct place and the cache has gone.
It is a great shame to archive this cache, however, the hollow tree was clearly not a secure enough hide. I hope the photos and logs for this cache will encourage someone else to place a new cache in a better place on Ile aux Cerfs in the future and bring other geocachers to this little paradise.