A few years back we had a banjo and a melodeon stolen from our car. We went round the local second hand instrument shops and found them very helpful in recovering the instruments.
The people who had stolen the instruments did not have ANY IDEA of the value/price or even what the instruments were. They were just interested in getting some cash and out of the place as fast as possible. The general opinion of everyone we spoke to, including the police, was that they were simply after cash to buy their next fix of whatever drugs they were on.
The bano turned up at a shop which sells mainly electric guitars. The bloke behind the counter had realised that it was stolen, as they didn't have any idea what it was, but if he had mad a fuss, they would have walked out and the instument could have been lost forever, so he gave them £20 for it. He then searched through the case to try and find means of identifying the real owner. When we turned up, he had already spent the morning phoning pubs which had numbers on advertising flyers for folk stuff, to try and put a name to the description of the banjo. He had even got as far as locating the phone number for my parents, where but nobody had been at home to take the call.
In the circumstance, for a hand built (by me) totally irreplaceable instrument, we were only too pleased to reimburse the cash he had paid out. He also had a photocopy of an electricity bill which identified a name and address for one of the group.
He was fairly certain that they had been carrying a case matching the description of the melodeon, and that they had been intending to take it to another nearby shop which has squeeze boxes and folk stuff in their window displays.
When we visited other shops we gave them permission to offer a similar amount of cash if it meant that the melodeon would be safely back in our posession.
Our biggest mistake was in informing the police that we had paperwork identifying the culprits. The did not do ANYTHING to help recover the items or the rest of the stuff stolen from the car - A car radio and a stack of cassette tapes, many of which I have still never managed to replace. When the melodeon arrived at the second shop, the shop owner telephoned the police with a description of the croup of thieves, the direction they were walking and all the information they would need for an imediate arrest and conviction. The police totally ignored it and did NOTHING. Their whole attitude was that the criminals were well known as local crooks and that they would not have the stolen goods at the address of the electricity bill. Because of this the were not going to even bother to look there. (We sometimes wish that we had not bothered to give the police the evidence, and instead gone to the address with a couple of ex-army friends and a sledge hammer to retrieve the goods or their value personally - we didn't, but sometimes wish we had).
Actually, the police DID try to do something. They decided they wanted to proseute the guitar shop for receiving stolen goods. Quite frankly we were disgusted, as it was only through the goodness of the bloke at the guitar shop that we had recovered my banjo. He never asked us a penny for returning the banjo, so if we had not offered, the shop would have been £20 down. We politely told the police to piss off.

My main point is that, although we know that a very expensive instrument has been stolen, it is more that likely that the thief does not. Unless the thief is a folkie (horrible thought), it is more likely to end up at a local junk shop than at somewhere such as Hobgoblin or Cleckheaton (by the way - as Gill Noppen-Spacie works at the Music Room, they will already know about it).

Quack!
Geoff the Duck.