Not sure what the demo dat rule is. Perhaps that there is a uniqueness to the stolen property? I see that dollars have serial numbers and now so do casino chips. So if the demo dat rule doesn't apply to seralized numbered dollars it doesn't apply to casino chips even tho now they have rfid tags internally (saw it on CSI used as evidence) so maybe the demo dat rule does apply to serialized numbered dollars. It likely applies to serialized numbered dollars having been marked with an explosive dye pack from a bank robbery.
Whether coins have numbers or rfid is not relevant in any way: this is exactly what I was trying to show by modifying the mugger-example... With most things property ownership is the most important value so your expectation holds: you get the exact stolen item back even if it means that later trades that were made with best intentions have to be canceled. The crucial exception is money and several things like it: When money is stolen, your property rights are _not_ the most important thing, security of transactions is the most important thing. This means if the mugger used your money to buy things at the store, you cannot get that money from the store: you need to get the mugger to give you the same amount of money instead.
It's possible that bitcoin will be considered a commodity in some court (I wouldn't bet on it), but I really doubt that applies in your situation. MtGox had the bitcoins, not you.