>Latin has
> traces [of the augment] like /e:st/ of course, but it evidently
> wasn't such a vital prefix in IE.
Happy to concede it wasn't a vital prefix, if you're conceding it was a
prefix.
But enough of that trail - Latin /e:st/ interests me. Are you suggesting
there was a Latin past form /e:st/ meaning "was"? You may well be right,
but it's new to me. The only /e:st/ I know is the present tense of the verb
esse = "to eat" (< *ed-t).