To get proof of having taken your flight, is to get your TA to print out the e-ticket copy of your ticket. When each flight has been taken, the online status will change from OPEN to USED. That is the only proof that you will have that shows that you took the flight as the coupon would have been used.

If you're missing BPs, usually a baggage tag will suffice...

But you need to first find out why your miles didn't credit. Can it be because that the fare basis does not earn you any miles in the first place?