Hmmm.... using '.*' as the search string would search the selected files one line at a time. From what you say, it would appear that this is correctly searching each file and returning the first match. As for using the text checkbox, the only time I would use that is to make sure I am not searching inside <...>.
. matches any character (except for line terminators)
* matches the previous token between zero and unlimited times, as many times as possible, giving back as needed (greedy)
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