Well he could have left one behind but then wouldn't Padme have had to hang on to it. Or at least keep it on her ship. seems a bit odd. I thought of maybe Obi doing some sort of force pull/ grab - but that seems pretty far fetched. I was thinking that maybe Obi wan would just stare on in disbelief and maybe yell out to Anakin, even though he can't see him "You were my brother" etc.

Part of the problem I guess is that Lucas rigged it all up at the end as though the next film kicks of straight away and not 17 odd years later, Making sure everyone winds up where they will later be.