"There are two verbs 「見える」 and 「聞こえる」 that mean that something is visible and audible, respectively. When you want to say that you can see or hear something, you'll want to use these verbs."
So, while the stem of みる would be み, the stem of みえる would be みえ。
The sentence is literally asking, "Has the teacher been visible?"
http://www.guidetojapanese.or
http://www.guidetojapanese.org/learn/grammar/potential
"There are two verbs 「見える」 and 「聞こえる」 that mean that something is visible and audible, respectively. When you want to say that you can see or hear something, you'll want to use these verbs."
So, while the stem of みる would be み, the stem of みえる would be みえ。
The sentence is literally asking, "Has the teacher been visible?"