Are retainer cases free?

Yesterday I left my retainer case in my 7th hour and I prayed that it was going to be there the next day. And today I checked and it wasn't there. I have my retainers but my case is gone. Are they free or are they really expensive like retainers or are they only like 5 bucks
Update: Also I woke up sick this morning and being unable to find it got me riled up and I had to look for my glasses for 10 minutes and Now I feel even worse

Also my orthodontist appointment is tomorrow at 9:30 am
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