One of the big problems with museum thefts is that they are often never reported. I know of several cases recently where the museum "officials" don't want to admit they lost something so just say it's "no longer on display." About 25 years ago the Pennsylvania State Police broke a ring that specialized in stealing Civil War guns from local historical societies. Many of them still had the museum tags on them identifying where they came from but when the police called to return them, some of the museums denied ever having them! There was a similar case recently where a CW presentation sword was stolen from Brown University. They never reported it and when it was offered for sale openly, and bought by a collector with a less than sterling reputation, they had to go to court to reclaim it. He, the collector, claimed that since they hadn't reported the theft he should be able to keep it. Thankfully, that was not accepted but the museum was complicit in covering the theft up.