watchとlookの動作イメージの違いについて
下記にan eldery woman's shoplifting を目撃したことを話すmailの文章があります。動詞を適語にして文を完成させます。
I was buying a new alarm clock the other day in Taylor's the jewellers, whan I actually saw somebody shoplifting. I'd just finished paying for my clock and as I turned around, an elderly woman was slowly putting a silver plate into a bag that She was carrying. Then she walked( was walking) over the another part of the shop and picked (was picking ) up an expensive-looking watch a number of times. when she thought that nobody was looking (looked), she dropped it into the bag. before I had a chance to tell the staff in the shop, She noticed that I was watching (watched) her and hurried out. Unfortunately for her, two police officers was walking past just at that moment and she ran straight into them.
上記の文の中の was looking とwas watching のみが正解らしいのですが、looked とwatched も それを最初から最後まで目撃したよ という意味ではlooked とwatchedもありだと思っています。 臨場感を考えると過去進行形しかありえないのでしょうか?それともlookとwatchの根本的な意味を間違っているのでしょうか?教えてください。