NPatricia, I think you must be playing Dr. Lynch ... in the tea room, completing the menu
I didn't find all the letters either, but it's optional, not required to finish the investigation. Some of the options were too difficult and I just abandoned them, like the one to line up the nuts and this one,the tea menu. Others were quite easy ... the hummingbirds and the statues on the mantel, and making coffee at the police station. I only struggled with them if I needed an extra hint
I liked this game a lot and am playing for the second time. The credits are fascinating ... all those Russian (?) names.