This leads me to believe that John Thorpe only knew the General by sight from the Bedford, as someone has already suggested. (As JulieW has pointed out more than once, JA tended not to drop hints like the Bedford into her writing for nothing, so I think JT really did know him by sight from there.) However, from the text you quote, it sounds like this is the first time they've had an actual conversation (though I think they may have been introduced and been on nodding terms previously).