Final answer for the I-94 card

Here is the answer I find from a website talking about I-94 card in the case that it is still in the passport when you come back to your country.

Please read and keep in file.


If you returned home with your Department of Homeland Security Bureau of Customs and Border Protection (BCBP) departure record Form I-94 (white) or Form I-94 (green) in your passport, it means that your departure was not recorded properly. It is your responsibility to correct your timely departure from the United States. This will close out your earlier record of arrival to this country.


If you do not validate a timely departure from the United States, or if you cannot provide proof when you next apply for admission to the United States, the DHS may conclude you remained in the United States beyond your authorized stay. If this happens, the next time you apply at the border to enter the United States, your visa may be subject to cancellation or you may be returned immediately to your foreign country.

To validate your departure, the INS will consider a variety of information, including but not limited to:
The green or white Form I-94 that you still have in your passport;

Original boarding passes you used to depart the United States;

Photocopies on entry or departure stamps in your passport indicating entry to another country after you departed the United States (you should copy all passport pages that are not completely blank, include the biographical page containing your photograph) and;
Photocopies of other supporting evidence, such as:
I. Dated pay slips or vouchers from your employer to indicate you worked in another country after you departed the United States,

II. Dated bank records showing transactions to indicate you were in another country after you left the United States,

III. School records showing attendance at a school outside the United States to indicate you were in another country after you left the United States,

IV. Dated credit card receipts, showing your name, but, the credit card number deleted, for purchase made after you left the United States to indicate you were in another country after leaving the United States.
Your statement will not be acceptable without supporting evidence, such as noted above.

In addition to your statement, you must include supporting evidence, as noted above. You must mail legible copies or original materials where possible. If you send original materials, you should retain a copy. The INS cannot return original materials after processing. To help us understand the situation and correct records quickly, please include an explanation letter in English. You must send your letter and enclose information only to the following address:

ACS - INS SBU
P.O. Box 7125
London, KY 40742-7125
USA

Do not mail your departure Form I-94 or supporting information to any United States Consulates or Embassy, to any other INS office in the United States, or to any address other than the one above. Only at this location are we able to make the necessary corrections to INS records to prevent inconvenience to you in the future.