There are two separate questions:
A. Whether you have a valid e-ticket for each segment.
B. Whether you are traveling on one e-ticket or two (even three).

If your e-ticket number was present and is now missing, I would not bother calling anyone other than MU as it is only MU which can explain how it was that you had a ticket and now you do not. MU's US line should be open. But, if it is not, then waiting until tomorrow is your best option. Note that you may call the US over Skype or any number of VOIP services at somewhere between free and miniscule amounts.

If you are on two tickets, remember that the risk of misconnecting is 100% on you. This is occasionally why these tickets are cheaper.