Gothic 3 Missing NPC - Diego

in my quests at Varant, i had Diego tagging along with me. but in one incident near Lago, while fighting the Bloodflies, Diego disappeared.. i teleported back to Braga & the text appeared "Diego is waiting.." but he is nowhere to be seen! how can i get him back and also is his presence necessary for any later quests?

Easiest method would be to use the console to teleport to him.

this is the second time that a NPC had gone missing. the first one is Karlen at Nemora.. if i could help it, i'd like to avoid the Marvin mode especially if he is not required in later stages..