Endermite Despawning (With nametag)

[XKaiserX]

So myself and GroovySoap made an endermen farm and were instructed to use an Endermite as bait for the Endermen. We were successful for a little bit with this method However the endermite despawned after a bit. It had a nametag and was in a Minecart. Is there any fix for this because having the ender farm was a very cool resource and i was instructed it should work.

Thanks.

 

[Orange]

Instructed by who?

This is a very odd way to bait enderman. 

There shouldn't be a reason as to why it despawned unless someone manually did a lag area or killmobs command near the area.