URGENT: Which I-94 I should present at departure from US

Dear Friends,

I came to US under F1 and had my status transferred to H1B in 2005 within the US.

In 2005, I took a business trip to Canada and did not turn in my I-94 (F1) at departure as I was advised that it is not necessary while traveling to Canada/Mexico and returning to US from Canada/Mexico. Then I got into a trouble when landing US from Canada: the customs officer almost rejected my entry, since I did not apply for a H1B Visa Stamp when I was in Canada for the re-entry (my company’s lawyer advised that I don’t need to), fortunately, he let me go. However, he took away of my original I-94 (F1) and did not put any admission record on my passport nor on my I-94 (H1B), I was afraid to challenge him if this is being done properly, since he was very pissed at that time. Anyway, he did take my fingerprint and photo, and I kept a copy of my I-94 (F1).

I reported this to the company’s lawyer, and she told me this is not something I should be worried about, as long as the officer let me enter, it means my entry was permitted legally.

Now I need to take a trip to China, which I-94 should I left at airport in order to record my departure properly.

Please kindly advise.

Sincerely,