Well at least you asked - so he's either thinking "what a nice person asking if I needed help" or "what a &*%er., I said I needed help and they rode off"!
I generally always check whether people are okay and need help. Sadly, a lot of people won't admit that they do need help, but it's always good to check (I have had it on laps of Richmond Park where I have asked someone and they've said they're okay, and 20 minutes later I pass them again - I stopped and forced some help on a lad with a snapped chain who had then threaded it back through his rear mech incorrectly once - I got him on his way).
I'll admit having been in the same situation - it can be hard to hear sometimes, so I have assumed that they are okay, possibly incorrectly.