how do i tell my girlfriend i think she might have eaten her engagement ring?

M30 and F29.

We have been dating for about 4 years and decided to pop the question during dinner last night. i asked the staff at her favorite restaurant to hide the ring in a brownie so she would find it mid bight and id propose. ( i see in hindsight now how much of a bad idea this was it seemed like a good idea since we met over a bake sale over brownies)

so she took a few bites about 4 and it looks like she chewed and no ring came out. i asked the manager i gave it too ( a personal friend of mine) if he put the ring in the brownie and he confirmed that he put it in right before he brought it to the table.

i asked him to look everywhere just to make sure i mean accidents happen but its either the ring dropped somehow or she ate it and my friend told me that the ring is no where to be found. asked him to look every where and nothing still im kind of freaking out and i dont really know how to tactfully tell her this.