catch off-guard

"The Power of Habit" を読んでいます。
Eugene Paulyは脳に障害があり、新しいことが全く記憶できなり、数分あるいは数秒前に起きた事、聞いたことも直ぐに忘れてしまう状態でした。
A few weeks later, his daughter came to visit. "What's the plan?" Eugene asked when she arrived. She took him outside in a wheelchair, onto the hospital's lawn. "It's a beautiful day," Eugene said. "Pretty nice weather, huh?" She told him about her kids and they played with a dog. She thought he might be able to come home soon. The sun was going down. She started to get ready to take him inside.
Eugene looked at her.
"I'm lucky to have a daughter like you," he said. She was caught off-guard. She couldn't remember the last time he had said something so sweet.
"was caught off-guard" の意味は "guard" がガードが甘いなどと日本語にもなっているので分かりますが、ここでは動詞の "catch" が受身で使われていますが、"off-guard" には普通どの様な動詞が使われるのでしょうか？　"off-guard" を辞書で確認します。
・Collins Dictionary: not expecting a surprise or danger that suddenly occurs ⇒ The question caught her completely off-guard.
・American Heritage Dictionary: Off one's guard; unprepared: a quiz that caught the class off-guard.
・Wiktionary: Alternative spelling of off guard: Not vigilant; unprepared; inattentive. His sudden appearance at the office caught her completely off guard.
例文で使われている動詞は "catch" だけでした。次の辞書には "off-guard" の項目はなく、"off guard" で次の説明がありました。
・Oxford English Dictionary: Unprepared for some surprise or difficulty: the government was caught off guard by the unexpected announcement
"catch someone off-guard" は慣用句として覚えた方が良いようです。
・McGraw-Hill Dictionary of American Idioms and Phrasal Verbs: Fig. to catch a person at a time of carelessness. Tom caught Ann off guard and frightened her. She caught me off my guard, and my hesitation told her I was lying.