Prior to this sentence, Kawashima was talking about jumping from the school's roof with Obata-sensei; aftwerwards, another teacher is speaking with Obata, and says:
小幡先生はひょっとして、自習時間に川島さんが話していたことを小耳に挟んで、だから不安になってらしたのじゃありません?
I'm guessing the 不安になってらした
means "became worried/uneasy", but I can't understand what's らした
's meaning.
Also, is じゃありません?
like じゃないか
, so like asking "isn't it?" rather than denying? So the whole sentence sounds like "During the free study period you happened to hear Kawashima speaking, so you became worried, isn't it?".
I'm having quite some difficult following this story so I'm not sure: on one hand it sounds right, on the other Obata did hear Kawashima - Obata didn't just happened to hear, Kawashima was speaking directly with Obata. It could be a roundabout way to say Obata knows what Kawashima said, but I'm not sure.