I too purchased several tickets this week, including more than international ticket by phone, but nothing I did was particularly complicated. I called because I wanted to confirm upgrades at the time of booking (which I did successfully).

Sometime within the last 24 hours I had a an eCredit appear in my account that I noticed this afternoon. Mine was also for one of the international tickets I purchased by phone and it appeared to be selectable this afternoon, although I didn't try beyond noticing it and noticing that it *did* have the checkbox. I clicked on the "ticket number" and found no identifying information, although the price did look suspiciously familiar.

However, in my case, the ticket was in the reissue queue to be reticketed in OP class and I suspected that was the problem, namely that the reissue was being processed and the credit appeared between the first ticket being cancelled and the new upgraded ticket being issued. My eCredit disappeared on its own without my intervention in late afternoon or early evening, significantly before the time of the OP here, although it's possible that a Chisholm elite phone agent noticed it during a call and corrected the problem without pointing anything out to me when we were discussing that PNR during a phone call.