The OP is completely right checking the ticketing process. I once was was on a DONE4 eTicket trip westbound from Europe to the US and then on to Australia, up to Asia. The ticket was issued by IB and I had flights on IB, AA, QF, CX and BA. Everything went well until I wanted to check-in for my first and only CX leg on that trip. They could find the booking, but not the eTicket. Of course, I had a printout of my eTicket, but they still couldn't find it.

The station manager was called and tried to contact IB. Now this was 9am in KUL and 3am in MAD. So he couldn't reach anyone. Finally, he decided that since I had credibility of having flown so many segments of that very ticket, also he could see the ticket in viewtrip and I was a OW Emerald, he will provide a hand written BP and take me onto that flight to HKG.

Obviously I reported this occurence to management level of our corporate TA and they took it to management level of IB. It appears that the error happened when IB sent the respective eTicket coupons electronically to all the carriers. They could prove that they had sent all coupons - and all but CX received them. However, the electronic message to CX never arrived and this apparently triggers no warning ...

So to be 100% sure, you have to check with all airlines involved, I'm afraid.