Missing playback

Why after I watched a replay it disappeared??? I had an alert about a pet, I watched it but when I went back to show my daughter 10 mintues later it was gone.

Do you have any filters turned on? At the Top, you can see if a filter is on by the blueish color indicating it has been selected, similar to this:

I selected Person so you can see the color change, if any of the items on this line is colored in, then you have a filter turned on: