Did my kid swallow this and if so what do I do?

I had this sitting on the banister. It had three of the pieces I’m holding.

My mom was here while I went to an appointment, while someone hooked up our cable, and knocked the mouth piece down. She said that she doesn’t remember if the guy picked up the piece or not. She didn’t look for it until he left. I tried looking and couldn’t find it.

Well apparently after I put the piece on the table, my mom put it back on the banister. This morning I was putting dishes in the dishwasher and I walk through to see if there was any more dishes left on the table and so I glanced at him and he had the mouth piece up to is mouth (he doesn’t like the mask his dr said to use it like that) and I look and another piece is broken. He apparently knocked it down with one of his toys. I put him in his high chair and frantically search for the piece, broke off the last piece and slammed it on the floor to see if that could help me find it. I picked it up, then I got down in that area too and swiped all over the floor and I still haven’t found it. I’m guessing he did swallow it. He’s not choking or anything or acting in pain, but I’m scared it might have a sharp edge or something. Should I call his pediatrician or take him to the Er? Omg I am freaking out.

They said if he starts having difficulty breathing to take him to the Er, but since it’s plastic it should pass through.