If you are panicking, don't, the VMs are likely still running and are just fine!
This is part of the reason I chose esXi, the great support for problems both by VMware and the online community in general.
Just SSH in and run the following. This fixed 5 invalid VM's for me with no hiccups, in under 1 second.
Note: If they keep comming back, you should probably diagnose why, but for me, I'm going to start by running this and see if that resolves my issue. Still not 100% what happened, but I read about large NFS datastores possibly having something to do with it. Which I have.