I have "new" memories all the time and usually only small pieces of an event. You know, some come out and I push them back and then they come back years later. I would think something triggered the memory. I would think that talking to your alters would help you to piece your memories together if your communication is open and they are willing to talk. But for me, I have absolutely no communication between mine, so I have to let my "new" memories go. I know there's not a likely chance I'll remember. The one time I tried to talk to an alter about a piece of a "new" memory, I was screamed and cursed at, so I gave up. If they think you're strong enough to know at this point, they'll probably help you remember, but if not they'll do their job to protect you and the memory of the event for your own good, until you're ready.