Thank you for the responses. I thought I was able to snap it in there before but I guess it wasn't. I had really given it some strong pushes too and used a screw driver try to jimmy it out to make sure it was secure and it seemed like it was.

I am not sure if it is relevant but I also just changed the exhaust system on it and while it's breaking in it has really vibrated the car when driving. I am wondering if that somehow just vibrated it out because it had been fine for 2 months previously.

Ether way though I think I will try to extend the flat washers that hold it in place and see if I can get a more defined snap. If not I will probably just use a silver twine to hold it in haha. Mainly because if it falls out again I will be buying my 3rd pair of lower grilles haha. Though one of them hasn't fallen out yet its just one side that keeps doing it.