"1) Surely the thieves can be traced by whom the points were credited"
Yes, they can be, but they probably won't be. £51 just isn't worth the effort for either the banks or police (and any insurance companies involved, who may be tied in with the bank), especially where there is probably a "cross border" crime. I.e. the person with your details could well be sat in his / her living room in the US.
Sorry to hear about it though. Most banks are pretty quick to refund money in these cases, especially if you've queried it straight away.