The officer does not need to take the document from you. It is also normal for them to have a supervisor review the notes of the interview and then make a decision within a few weeks to 30 days. Be patient. If you do not get a decision within 60 days you should make inquiries.
The answer provided here is general in nature and does not take into account other factors that may need to be reviewed for a more precise answer. You should consult with an immigration attorney before taking any action. The answer here is not intended to create an attorney-client relationship.
I agree with my colleague that the officer does not have to take the I-94 card or a document for that matter-different USCIS offices use different procedures with regard to what they take from the applicants and/or petitioners. Be patient and if you were truthful in your answers and have nothing to hide and your case should be approved.
The USCIS office in Houston office will take the I-94 card from an applicant for Adjustment of Status (green card, essentially), especially when they approve the case on the spot (which they do only rarely nowadays). That said, there is no requirement under the law that I am aware of that would require their taking your I-94 card. It sounds as though you'll get a result in the coming weeks. Good luck!
It is not required that the officer take your I-94 card. Most officers do, but the fact that the officer in your case did not is not a reflection of your case by itself.
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