Earlier quoted context omitted.
It becomes complicated if the new owner has legitimately bought the bike in a second hand store.
It's not that complicated, legally speaking. The rightful owner gets to get their stuff back, and the new "owner" has a claim against the purveyor of stolen goods for the purchase price.
The new "owner" will keep the bike as he has bought it in good faith. The shop will claim that it cannot check every used bike. The rightful owner could try to get money from the person who stole it (if found), but they most likely don't have any money.
It's the perfect crime and the reason why we cannot have nice bikes. People are literally sleeping with their expensive bikes in a room.