いるのが見えた

could see someone or something doing something

→ 居る
phrase Rare #24,301
could see someone or something doing something Used after a person or thing plus a ている phrase to say that the speaker saw them in the middle of an action or in a certain state. 見えた means “was visible” or “could be seen.”
JA: 遠くで鳥が飛んでいるのが見えた。
EN: I could see a bird flying in the distance.

ある人が素手で掘っているのが見えた

I saw someone digging with their bare hands.

大きな犬ヒルさん家の前で寝そべっているのが見えた

I saw a large dog lying in front of Mr. Hill’s house.

大勢の人が野球場急いでいるのが見えた

I saw a large crowd of people hurrying to the baseball stadium.