so the problem is on their side, how would it be possible to withdraw bitcoins from your bittrex account without sending email with link to the withdrawal authorization?
In general situation, it is possible that the site sent an Email, but the hacker was able to access the Email account and deleted all the traces.
However, in OP's situation, it's quite weird because his email account was tied in his mobile phone which makes it harder to hack. Just want to clarify about this:
5. My gmail need mobile verification to login, an on those time I did not have to confirm any new location Gmail login
@OP, does this mean that if you're in the same location or something, you don't need a verification?
Mobile verifications will most likely to be asked when you are logging in into a different location or simply a different IP but when you logged in on your own IP then you wont really asked for mobile verification.
No matter which angle i do saw on the situation only the access on email would really be the hole on such compromised incident. Hacker might able to access the email and deleted history of logging in notification just as mentioned above.