I am an Australian citizen currently on a B2 that expires in Oct. I lodged I-539 application for extension in Aug and received I-797 receipt Aug 25.
I may have found an employer that will sponsor me on an E3 visa (Australians only). All I need is a letter of offer and a completed Labor Condition Application.
To apply for the E3 visa though, I need to leave the USA and visit a US consulate. I do not have my original I94 any more (I submitted it with my I-539) but I do have a copy of it. Once I get a letter of offer, I will travel to either Toronto Canada or home to Sydney Australia to apply for the visa.
Qo1. Can I still leave the USA without the original I94?
Qo2. In the event my E3 visa is denied, will I be able to re-enter the USA from Canada without the original I94, provided my stay in Canada is less than 30 days? (And how would this work if I take the trip up there after the expiration date of the original I94? Remembering that my B2 extension is pending)
 Ans1. Yes. You should not need an original I-94 to travel out.
Ans2. Â You probably cannot reenter using a copy of the I-94. Not only that, your departure from USA renders your pending B application void (considered abandoned).
They way I see it, you have two choices. Wait for B extension before you go for E stamping. Or, go for E stamping bearing in mind the consequences of abandonment and reentry not assured.