How would you spell it phonetically without using an r then?

I would have to hear the speaker say the two phrases, before attempting to transcribe them accurately. I was just saying that some non-rhotic varieties of English use an r in phonic spellings to indicate difference in vocalic quality, and not that there is anythingr-colored about the vowel. On the other hand, some non-rhotic varieties of English exhibit a phenomenon called intrusive-r, where an r intrudes in a word, where it is not phonologically or etymologically motivated: e.g., pronouncing barn /bɑːn/, but idea /ʔəjdiːɹ/ in some varieties of NE US English.

Ceci n'est pas un seing.