Had another RP have the GM vanish. We have three options really. 

1. We wait for the GM to come back
2. We say it's dead and move on.
3. Someone else takes over and acts at the GM.

I'm currently in an RP that had this happen and we went with the last option and it's still running pretty good. I would step up but I'm not sure how well I can run a RP on my own. The real issue with starting a RP is needing to have someone else to back you up and keep things running so it's not all sitting on one person. Things happen and you might get busy, or maybe your PC dies or Internet. I'll give it some thought on what I want to do. Running an RP is not an easy task.