Wouldn't He know the answer to this question since He was God the Son, part of the Trinity?
Mark 5:30
ESV - 30 And Jesus, perceiving in himself that power had gone out from him, immediately turned about in the crowd and said, "Who touched my garments?
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My opinion is that followers of Jesus come in different ways. Some simply join other Christians (form a cloud see Mark 5:31) without seeking anything from Jesus or having a clear understanding of Him. Spiritually they squeeze Him by being so just as they physically appear. In the spirit, Jesus saw the woman tap ( or touch as opposed to squeeze) from Him his power. Many physically touched Him as the disciples saw them do so and therefore they could not just single one as a response to Jesu's question!. Jesus wanted to tell disciples that among the many people that rubbed shoulders with, He did not notice they were there except the only one woman who had an understanding of His attributes.