Part of the fender on 2003 Toyota Echo pop out. Is there some kind
Of clip or plug that may have broken?

Many of today's cars are snap together, so, yes, if the vehicle was in even a slight fender-bender, it likely has a broken retainer.
Maybe your local dealer can provide a picture of the affected area that shows the type of clips or retainers.

Thanks

Typically, those are composite materials which snap together. It clearly looks like your's fractured.

As was stated already, looks like part of it actually broke. I have had this happen on cars before and was often able to use plastic cable ties to hold the pieces together. If you can get your hands in there (maybe from underneath) you might be able to hold it together with a cable tie or 2. Occasionally I have had to drill pieces to give the tie something to wrap around.

Very good idea, Odinn7.