What would I have done?
I'd have phoned somebody who had a manual. Or gone to see if there was one about the airfield I could borrow. Or for that matter looked it up in the POH I had on board, since I might well keep a copy as a matter of convenience.
Or dare I say it, used the "external power start" bit from the official checklist, which I'm pretty sure is there.
Stuck on the ground without the POH to look something up might be inconvenient, but it's unlikely to jeaopardise flight safety, as in that situation or most similar ones, you have the option not to fly.
But in flight? A pilot should be flying, or landing his or her aeroplane if they have a problem, and anything they really need should be either in their heads, or the checklist. I can think of very few, if any, occasions where you should be looking anything up in the POH in-flight, in a single pilot aircraft. And therefore, I do not see carrying a POH in flight as having any flight safety benefit - and if it doesn't, why mandate it?
G