"I do not find my phone."
Translation:Ní aimsím m'fhón.
It doesn't like ní aimsím either… Yes, Duolingo isn't testing on knowledge, but it's not teaching adequately if it marks acceptable usages as wrong. Discussing sentences in this way gives the makers of the course a chance to add usages.
I'm confused why "mo" is shortened here. I always thought that it was only abbreviated to " m' " when the next word started with a vowel.
The lenition of fón to fhón caused by mo silences the sound of the F, leaving only the “ón“ sound. Since that remaining sound begins with a vowel, mo becomes m’ — hence m’fhón.