My first two had CP and we were in no doubt. With #3 I wasn't sure as there some small spots that seemed about right and went through the process but weren't really large enough to be sure. About two years later he had chicken pox for certain but it was not severe like my first two.
I know you wanted answers from 'only 1' but as there weren't any answers, and I reckon most people wouldn't see it as CP and pass it off as a bite, I thought I'd butt in. I think even if it is CP he won't have immunity and will get it again.
By the way when I got it, the first lump was on the back of my neck and then went down my jawline.
Robynne-69 DH-61 DS1-94 DD1-96 DS2-99 DS3&DD2-04