what did i do wrong?

hit the waters of one of appalachia's treasures- the new river- this (early)
evenin. other than a brief encounter involving an invitation to join some
fellas who were headin down the river in canoes to do a little fishin, i was
had the stream all to myself.
i had been fishing there last week, with a woman that my instructor hooked
me up with, so i hit the spots that she had success with in the past. i
only had about an hour to spend in the water, as i had a friend coming in
from out of town for to spend the evening. so, in i went. i hit the "hot
spots" first, where i got a little action, but nothing significant. after
about a half an hour, i noticed that the fish were jumpin out of the water
one after another just upstream a little bit, so naturally i headed up to
stalk them. when the fly i had tied seemed to have worn out it's welcome, i
put on a sulfur. i thought that with all this activiy, i would surely hook
one. instead i spent the next half an hour frustrated as i watched fish
after fish come out of the water to feed, but only got a couple of strikes.
i keep thinking that if i had been able to stay longer, i would have gotten
something, but i can't help but wonder what i was doing wrong. maybe just
not picking out the right fly? i know it's hard to say without being there,
but any ideas? i don't think i spooked them, because they didn't go
anywhere. they just continued to taunt me :-(
help- snake