"in case something was wrong" or "as if something was wrong"?
Last December，just a week before Christmas，I went to a local KMart store to pick up my layaway．Upon reaching the counter, I handed the clerk my layaway receipts and told her I was there to pay off the balance and take the goods home with me．She grabbed my receipts，and kept messing with the computer ________ something was wrong．I felt a little uneasy．I was expecting her to tell me my layaway had been misplaced or something of the sort.
It is a cloze test. May I ask why can't I say "in case something was wrong" because the key is "as if something was wrong"? Thank you.