I didn't take screen shots, but here's what I believe happened.
1) I was working on my last quest for a credo. It was a 4-part quest - one was a delivery to a quest giver, and another involved studying an object.
2) When I logged out, I'd done everything except for the studying part, and the needed curio was in my study area
3) When I logged back in after enough time to finish the studying, I got the usual message one gets when a quest _fails_ because a quest giver has been destroyed.
4) I did NOT get a message about the credo or its quest completing, let alone information about the replacement quest
5) When I checked, I found no quest associated with the credo
6) And on farther checking, found that the credo was complete.
The bug is the message in #3.
I don't have a screen shot - didn't think to make one.
I was using Ender's beta client, not the official client. I don't think the client should effect anything here, and in any case I can't retry with the official client. So I'm posting this for whatever it's worth, if anything.