Hi Rob.

It doesn't matter if it's in good faith or not; the buyer was receiving stolen goods (whether they knew it or not).

Depends on what happened. If it got stolen, then you are right. However, german law seems to indicate (from the quick browsing of relevant paragraphs I just did, german law: BGB §§986-1003,1007), that there is some order in the claims to be fulfilled.

Let's say A originally owned a good, B stole it from him an C bought it from B. If this is the case, A has the right to demand the good from C. However, C has the right to hold on to the good until his claims regarding this good are fulfilled (i.e. B paid him back). Also, A has the opportunity to demand compensation for the stolen good from B, but if he does so, he looses the right to demand the good from C. Compensation for the good itself left aside, A can always demand compensation for lack of use from B.
If A's insurance already paid for the good (and as such, A got compensated for the good) and C bought the good in good faith, noone can demand the good from C, neither B nor A's insurance.

If the good was lost, and C found it, C must deliver the good back to A, but has the right to hold it back until he got 3-5% of the goods value (5% on values below 500EUR, 3% above 500EUR and for animals) plus his expenses.

If the good was lost, found by B and bought from B by C, it get's more complicated again (but similar to the first (theft) variant, except A can't demand compensation for a lack of use).

Also, if the good was lost, and C found it, C has to indicate his finding to the appropriate governmental agency. Six month from the date of indication of the finding, C gains the full rights on the good, no matter what, even if B stole the good from A and lost it.
In other words: If you buy some stolen good (even in good faith), and the original owner finds you and can proove his rights, you are loosing the good. If you find a stolen good (and don't know it was stolen), and the original owner finds you 6 month and one day after you reported your findings to the officials, you keep the good. Obviously, if you know the good was stolen for some reason, or get to know that it was stolen within 6 month after your finding (and reporting it), you can't keep it.

And I really expect that Belgian law is really similar to german law.

cu,
sven