Where was Elisha when he sent a son of the prophets to Ramoth Gilead to anoint Jehu in 2 kings 9:1?
We're not told where he was. It's possible that Elisha was still in Damascus when he gave this message, since that is where he was the last time he was mentioned by the author (2 Kings 8:7). I don't think this is likely, given that Elisha is giving a message to one of the sons of the prophets, and its doubtful that this Jewish school had a branch in Damascus.
At this point in the narrative Elisha has largely faded from the scene. Like his predecessor Elijah, the end of his ministry is marked by the anointing of kings. Largely, the focus as shifted off of Elisha's prophetic ministry back to the chronicling of the kings of Judah and Israel. In fact, we don't hear about Elisha again after this until his death (2 Kings 13:14).
I think its important to ask questions like this, but in this case I think the omission is merely a reflection that the narrator has moved on his telling of Israel's history.