Who is it that touched me, Mark expresses it still more clearly, when he says that Christ looked around to see who she was. It does appear to be absurd that Christ should pour out his grace without knowing on whom he was bestowing a favor. There is not less difficulty in what he shortly afterwards says, that he perceived that power had gone out from him: as if, while it flowed from him, it was not a free gift bestowed at those times, and on those persons, whom he was pleased to select. Beyond all question, he knowingly and willingly cured the woman; and there is as little doubt that he drew her to himself by his Spirit, that she might obtain a cure: but he puts the question to her, that she may freely and publicly make it known. If Christ had been the only witness of his miracle, his statements might not perhaps have been believed: but now, when the woman, struck with dread, relates what happened to her, greater weight is due to her confession.

And Jesus said, who touched me?.... This he said, not as ignorant of the person that had done it, but in order to discover her to the people, and the cure she had received, as well as her faith; See Gill on Mark 5:30.
When all denied; both the disciples and the multitude, as many as were near him, and who might be thought to have done it; all excepting the woman, who afterwards came and declared it; for it is very likely, that as soon as she had touched his garment, and got her cure, she drew further off:
Peter, and they that were with him; the rest of the disciples, who were in company together, as appears from Mark 5:31
Said, Master, the multitude throng thee, and press thee, and sayest thou, who touched me? or "my garment", as the Ethiopic version reads; See Gill on Mark 5:31.

Who touched me?--"Askest Thou, Lord, who touched Thee? Rather ask who touched Thee not in such a throng."