Sorry to hear of your theft, it's really awful, isn't it ?
Regarding the medical certificate . . . . . . .
Medical - go back to your AME - he/she will issue a duplicate
is, of course, absolutely right. It's just worth pointing out, though, that in this hi-tech day and age almost
any AME could probably help, not just the one who did the last medical. So if your own usual chap is unavailable or on holiday, for example, any AME at all who uses the "
AME-online" system could access your details and print off a copy of your last certificate. He would need proof of ID (passport, etc), and your CAA reference number.