Hi Tom
numbness is a common symptom of anxiety though not one Ive had too much personal experience of. Have a good read through some of the older posts in the symptoms section and Im sure you will find people who have had it for days at a time.
Put it this way, I get chest pains as my main symptom and in the past have had them for a couple of days straight!
I did get to speak with a doctor about anxiety for an hour and a half last week which was amazing. What I learnt was that anxiety can mimic pretty much any symptom you can think of which is what makes it such a horrible illness. It constantly keeps evolving to trick you and make you panic more because its only fear which feeds it. As soon as you can stop the fear of whatever it is troubling you, the anxiety will go. Easier said than done I know and Im nowhere near there myself yet (why is it easier to dish out advice to others and not follow it yourself!? )
I would always advise you see your GP with any new symptoms you are worried about as it would be irresponsible for me not to say that but I would be pretty damn certain it is just anxiety or some minor such as a trapped nerve. This should hopefully set your mind at ease that it isnt serious.