Could be. Or does it simply mean what was remembered changed as time went on. When a stressful event happens like a little girl goes missing and people wish very much to help then even if they do remember something, what is remembered and its details can easily become skewed and change over time. And yes people can also remember things that were not there in some cases. But it is not a certainty that is what happened in this case. It is only one possibility out of many.
Even without stress memory can be tricky. Try this: Go to a restaurant with a room full of people and, if they let you, take a picture of the room full of people. Now eat your meal and then go out to your car and write down a description of everyone you saw at the moment the pic was snapped and what they wore and what they were eating and if they were carrying anything what it was.
Don't read it back when you are finished just seal it in a dated envelope.
Keep the picture you took sealed up in its own place and do not look at it at all until the end of this whole experimment.
Now repeat the writng and description part, trying to remember every possible new detail you can, in two weeks and again just seal it up in a dated envelope.
Now repeat the writng and description part again in a month from that last description, trying to remember every possible new detail you can, and again just seal it up in a dated envelope.
Now repeat the writng and description part again in two weeks past the last description, trying to remember every possible new detail you can, and again just seal it up in a dated envelope.
Finally sit down and open each envelope in order and see what happened to your memory and description of the events. You may be surprised at the results.
This is the end of the experiment so compare your writings with the picture. How did it go? Did you miss things that showed up in the picture? Were people there you had forgotten? Were people in different places or positions or dressed differently than you had written? Had your descriptions changed over time? Was any discrepency a result of you imagining things?
Let me know how it goes.