I caught both of mine doing the same thing. Not sure what interconnecting piece is supposed to be holding the thing in. I will have to scrutinize the exploding drawing very closely again. My solution was the same as already mentioned, just pushed it back in.
I looked at the aforementioned parts and found that the ejector has a long hooked arm on one side. When it is returned back into the straight up position the hooked arm fits into the slot on the front of the hammer pin holding it in place. Why the hammer pin likes to drift even when held in, I don't know. I found mine doing the same much like you did, the ejector would not return to the correct position. Not sure if the pin had drifted during firing or just while I was cleaning the gun. I just keep an eye on it whenever I'm at the range.
What is the solution? Not sure if there is one. A striker fired SR45 would eliminate the need for a hammer pin entrely....hint, hint!!!!