If you are a non-immigrant, when your travel abroad (except Canada or Mexico), the I-94 card is taken by the carrier. If I-94 card on the passport is expired in such a case, there must be a valid one (like your H1 approval notice).
When you get back to the US, you get a new I-94 card with your legal paperwork admitted by US immigration officer.
if you travel to Canada or Mexico as a non-immigrant, you need to show your I-94 card at US custom border to prove your stay in the US is valid because the I-94 card is not taken away. If the I-94 card on your passport is expired in this case, you need to show your H1 document to prove your validity and you will get a new I-94 card at the same time. If your I-94 card on passport is not expired, nothing happens.
So what matters is your legal validity of stay as a non-immigrant.