I've used the dismiss command on him to send him back to prim, however, upon returning, hes nowhere to be found, I didnt recieve his quest failed mission (an Indicator that he was killed), so he must be "alive" somewhere. I checked the Fallout new vegas Wikia and this is said to be a bug, if so, is there any solutions to fix this? I miss my lil' eye bot.

Yep has to be a bug, in my game ED-E can't even die he/she just gets knocked unconcious.

Im playing hardcoe mode (so companions CAN die). Hrrm, its this bug, and the one how everyone still says prim was taken over by ncr (despite me putting someone else in charge).