How does a stranger know I've posted a phrase on Twitter?

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A short while ago, I tweeted a reference to the artist, Edward Hopper (without hashtag). Two minutes later, a Hopper expert favorited my tweet.

How did she know about my Hopper tweet?

[976]

Because the search by still searches for phrases, not just hash tags.

For example, if you search "Edward Hopper" into the search bar, you will not only find hashtags, but also the name without 'em...