I moved my site to a new server and my site when down for over 24 hours. nearly 50% of my traffic was coming from stumble upon. After the move I have lost almost all of my stumble traffic. Can someone help and tell me if it will come back or what I need to do to get it back?
Unfortunately I think you will have to start over with StumbleUpon as it is a really user driven site. You just need to get some of your users back and the rest should follow shortly after though as you have already had some success with it.
You yourself have specified that your website was down for 24 hours so obviously you are going to loose traffic, but as its back now you will get your traffic back in 1-2 days of time