From your explanations I do not know how your funds was taken(you can try and explain better), were you trying to send to an address and sent to the wrong address. Maybe your private keys aren't as secured as you claim it is, did you write or store it somewhere that's accessible to someone other than yourself.
I just hope it's not just you sending to another address of yours, sorry I just get a bit sceptical when a line like this is added in this kind of post. If your mum is truly ill, you will have to find a different means of footing the bills.