Bike chain

I pass this bike every morning when I walk up for my newspaper.  It appeared here shortly after Christmas and looks to be fairly new and in good condition; indeed, a rather nice bike.  I initially assumed it had been left there by someone working nearby as it is securely padlocked to a metal fence.  However, after a couple of weeks the back wheel disappeared and the rest is still there several weeks later.  All a bit of a puzzle; if it had been stolen and dumped, why was it padlocked?  If it had been left there by the owner, why haven't they come back?  And if the back wheel was stolen, then why not the front?  It's not secured by the padlock and easier to remove than the back one which would have had the chain attached.  All a bit of a puzzle.  Where is Maigret when you need him?